Thank you to Yank. Definitions are underlined in the clues.
Across
1. Bowl of hot stuff with foul smell (6)
LAVABO : LAVA(hot fiery stuff from out of a volcano) plus(with) BO(abbrev. for “body odour”, a foul smell from out of an animal’s body).
Defn: …/washbasin.
4. Outspoken choice to be in love with ring combatant (7)
PICADOR : Homophone of(Outspoken) [ “pick”(choice/the best or the considered best of a group) + “adore”(to be deeply in love with) ].
Defn: …, a bullring, that is.
9. Techie wordsmith holds advanced degree (9)
WEBMASTER : WEBSTER(Noah, American wordsmith/lexicographer, and author of the now-named Merriam-Webster Dictionary) containing(holds) MA(abbrev. for “Master of Arts”, an advanced/post-graduate academic degree).
10. Having special powers but uncrowned, like ancient Greeks (5)
IONIC : “bionic”(of a person having special powers through mechanical enhancements) minus its 1st letter(but uncrowned).
11. Mr. Young’s beef? (5)
ANGUS : First name of Angus Young, Scottish born musician and founder-member of the group, AC/DCC
OR
A fellow/Mr. with the common Scottish surname, “Young” could very well be an “Angus”, a popular Scottish first name.
Defn: … from the Aberdeen Angus breed of cattle, originally from Scotland.
12. Language of sections of Rio eschewing contrived alliteration (4,5)
LATE LATIN : Letters of(sections of) “Rio” deleted from(eschewing) anagram of(contrived) “alliteration “.
(per Mallimack@3, and then others)
13. Renewal letter includes payment aid (1-6)
E-WALLET : Hidden in(… includes) “Renewal letter”.
15. Remnants of reversal of Jewish ritual? (6)
DEBRIS : DE-(prefix indicating the reversal of a process, as in, say, “dehydrate”) used whimsically to indicate a reversal of BRIS(the Jewish ritual of circumcising a baby boy).
17. Blonde, blue-eyed detectives and Harry’s pal lying about (6)
NORDIC : Reversal of(… lying about) [ CID(abbrev. for the Criminal Investigation Department, a department of detectives) plus(and) RON(Weasley, Harry Potter’s pal) ].
Defn: …, a stereotypical description of this particular racial classification region of Northern Europe.
19. Promiscuous sort of small bird? (7)
SWINGER : S(abbrev. for “small”) + WINGER(one with wings, a bird, say)
22. Thick-headed Genevan philosopher’s collection of bride’s clothing (9)
TROUSSEAU : 1st letter of(…-headed) “Thick” + ROUSSEAU(Jean-Jacques, philosopher born in Geneva)
24. Java, lacking kick, stood up to West (5)
DECAF : Reversal of(… West, in an across clue) FACED(stood up to/confronted).
Defn: Coffee (java in American slang) without the stimulation or kick provided by caffeine, in other words, decaffeinated coffee.
26. Beast with one horn that’s deformed (5)
RHINO : Anagram of(… that’s deformed) [ I(Roman numeral for “one”) + HORN ].
Some not with one horn, but two:

27. A migrant’s developed popular app (9)
INSTAGRAM : Anagram of(… developed) A MIGRANT’S.
28. Spa location uncovered in part of squalid digs (7)
RATHOLE : “Bath”(a famous spa town in SW England) minus its 1st letter(uncovered) contained in(in) ROLE(a characterisation/part that is played).
29. Faction of Minnesota legislature recalled dessert (6)
GELATO : Hidden in(Faction of) reversal of(… recalled) “Minnesota legislature”.
Down
1. Underhand tactic, fudging flaw before time’s up (7)
LAWFARE : Anagram of(fudging) FLAW placed above(before, in a down clue) reversal of(…’s up) ERA(a long period of time).
Defn: … of using the law to intimidate or hinder an opponent.
2. Early Porsche development: frontiers of UV waves on spyware (2,3)
VW BUG : 2 letters between(frontiers of) “UV” and “waves” placed above(on, in a down clue) BUG(spyware/hidden listening device).
Defn: Nickname of the early Volkswagen car developed by Ferdinand Porsche, German automotive engineer.

3. Bane: where kidneys may be found? (4,5)
BEAN SALAD : Reverse wordplay: Anagram of(… SALAD) BEAN = Bane.
Defn: …, kidney beans that is.
4. Breathily said: ‘Arsenic’s taken and bootlegged’ (7)
PIRATED : “aspirated”(pronounced a consonant with an audible breath/breathily said) minus(…’s taken) “As”(symbol for the chemical element, arsenic).
5. Stick ice cubes in prime minister’s rear? (5)
CHILL : Last 5 letters of(…’s rear) “Churchill”(Winston, wartime prime minister of the UK).
Defn: To ….
6. Deadbeat, leaderless knight errant to pursue mobster? Duck! (2-7)
DO-NOTHING : Anagram of(… errant) [ “knight” minus its 1st letter(leaderless …) ] placed below(to pursue, in a down clue) [ DON(a leader of a gang of mobsters/a crime syndicate like the Mafia) + O(letter representing 0/zero runs/”duck” in cricket scores) ].
7. Withdraw from drunken trance (6)
RECANT : Anagram of(drunken) TRANCE.
Defn: …/to retract, say, a previous declaration.
8. Probe small hovel? (6)
STYLET : STY(a messy living space/hovel) LET(a suffix indicating something small).
Defn: …/a thin rod-like instrument used in surgery.
14. Defender in a game point (9)
APOLOGIST : A + POLO(a game played on horseback) + GIST(the point/essence of some long passage).
16. Three vitamins removed from balanced diet, unwise fix-up (5,4)
BLIND DATE : A,E,C(three vitamins) deleted from(removed from) anagram of(…, unwise) “balanced diet”.
18. Drug dealer shortened Eastern undergarment (7)
CHEMISE : “chemist”(whimsically called a drug dealer) minus its last letter(shortened) + E(abbrev. for “Eastern”).
Defn: … worn by women.
19. Obliterate vegetable (6)
SQUASH : Double defn.
20. Moral of deviant: ‘That’s hilarious!’ (7)
ROFLMAO : Anagram of(… deviant) MORAL OF.
Answer: Texting slang for “Rolling On The Floor Laughing My Ass Off”, when responding to something hilarious.
21. PM expels head of monarchy, a rude sort (6)
STARER : “Starmer”(Keir, PM of the UK) minus(expels) 1st letter of(head of) “monarchy”.
23. Looms spinning at reduced speed (3-2)
SLOMO : Anagram of(… spinning) LOOMS.
Answer: Short for “slow motion” or reduced speed.
25. Around 5/9ths of what biorhythms are (5)
CIRCA : 1st 5 letters out of 9(5/9ths of) “circadian”(descriptive of a process that occurs in a 24-hour cycle, including biorhythyms/one’s biological clock).
Defn: …/approximately, when referring to years or dates.
Enjoyable, quirky offering today with a few laughs along the way. I liked PICADOR, ANGUS, E-WALLET, NORDIC, RHINO, INSTAGRAM, BEAN SALAD, BLIND DATE, CIRCA and ROFLMAO. Took me a while to parse CHILL, which linked nicely with STARER, after Donald’s snippy comments. LATE LATIN, LAWFARE and STYLET were new words for me.
Ta Yank & scchua.
I had a bit of a nightmarish time to begin with this morning. Could not solve anything but then slowly, slowly managed to chip away and make some progress with LAVABO in first. If I have a bad start I always lose confidence and then take forever to crack relatively straight forward clues. Otherwise, I was stymied by lack of knowledge of popular culture. For eg, I guessed ANGUS” but i’m glad to have confirmed that this is the Mr version is the Aussie AC/DC chap? Guessed the acronym was text-speak at 20d (and was helped by having heard a ruder version). Some more obscure (for me) solutions required some checking – such as STYLET and (DE)BRIS but a combination of logic, Google and crossers got me there. Overall ,I found today’s offering very tricky but, despite some rather agonising constructions everything parsed satisfactorily and now I feel a mixture of relief, amusement and gratitude for the workout. Thanks all round.
12 is an anagram of ALLITERATION minus RIO
LATE LATIN is an anagram, with the removal of the letters Rio in alliteration.
Thanks Mallimack. I’ve deleted my wrong parsing and put in yours.
12a is an anagram of Alliteration minus the letters rio
I parsed LATE LATIN as an anagram of ‘alliteration’ less) eschewing) the letters R, I and O.
Thanks Yank and scchua
I gave up on this one, which I very rarely do. I don’t recall a Guardian puzzle that included so many things I’ve never heard of – LAWFARE, ANGUS Young, VW BUG, for example. (There were more, but I won’t list them all.)
Ferdinand Porsche was the lead designer of the Volkswagen Beetle. https://en.wikipedia.org/wiki/Ferdinand_Porsche
Thanks for the explanations. Most of this went in reasonably comfortably, although I was defeated in the NE corner: 12a, 4d and 5d eventually went in because of crossing letters, although I couldn’t parse them for the life of me, and 8d (a new word for me) was left unfilled. I also couldn’t see the (now, after explanation, quite obvious) parsing of 26a.
I enjoyed the cluing overall, though I’m slightly dischuffed by 20, as I don’t like acronyms (which this isn’t even really, as it’s impossible to say as a word) being clued in crosswords as though they were words. Perhaps “Moral of deviant: ‘Initially, that’s hilarious!’” would have soothed my brow.
I think Mallimack @3 has it for 12a – that makes complete sense. Thanks!
Edit: oh, and while I was writing this, so have several others!
Enjoyable, more please! I especially liked the non-standard stuff: CIRCA, LATE LATIN, BLIND DATE, BEAN SALAD. Also virtual ticks for DECAF, APOLOGIST, DO-NOTHING, CHEMISE. ANGUS is of course Malcolm’s brother of AC/DC fame. Thanks Yank and scchua!
VW BUG is the frontier (i.e. border between) (u)V and W(aves) + BUG.
Ever have that situation when despite having early checkers for a solution you just know you’re going to have to make the journey round the entire puzzle to get the final checker(s) and so reach the answer (often as LOI)? That was me with TROUSSEAU.
Solid stuff overall, and I particularly enjoyed CHILL, BLIND DATE and indeed the misdirection regarding Mr Porsche, which I could only surmise at but which was readily confirmed. Alas I couldn’t parse DEBRIS.
Thanks both
I liked the idea of Mr Ferdinand deciding not to say “Simply stellar strike from super Stones”, but in the cryptic grammar isn’t the alliteration eschewing Rio?
Tough to get into but made it in the end. For 20D I think it is Rolling On The Floor..?
Thanks to S and Y.
Thanks to Andy @12 for explaining how the compiler got VW which I had failed to grasp. I found the parsing of BLIND DATE particularly tricky – confronted with fodder containing 6 vitamins, I’m not quite sure how I am meant to identify the 3 to be deleted before anagramming the remainder. I am hopeful that 20d is the only time I encounter ROLFMAO but, if that’s the kind of entry that will pull in hordes of Gen Z solvers, fair enough.
Thanks both
Simon@15 @scchua
And would it not be ass rather than arse? Is it not an Americanism?
I took a terrible beating today, especially when cornered in the north-west.
However, bloody but unbowed, I’ll try again tomorrow.
Thank you, Yank and scchua.
Surely the def for LATE LATIN is simply ‘language’. ‘Language of sections’ doesn’t seem to mean anything in particular, unless it’s meant to refer to Roman provinces.
poc@19, that’s how I had it, yes. The “sections” of Rio being the individual letters, which need to be removed independently since “rio” is not a substring of “alliteration”.
petert@14: eschew as in to abstain from or refuse to participate in.
So not the Jewish SIRBED ritual then 🙂
Thoroughly enjoyed having to think outside the UK box. I thought we might be in for a major quibblefest but thankfully not
Cheers S&Y
Too many googles means this was more of a slog than a pleasant test. Thanks both.
I always think that Paul Whitehouse is Harry´s mate
Sid Junior @23
I was wondering whether it was Tom or Dick!
Just to say, to save any fellow-countrymen doing so, that at Scottish seats of learning an MA is a first degree. Also, while I’m here, I was familiar enough with LMAO (sometimes expanded to LMFAO) but had never come across the ROF- elaboration, but the anagram clearly required it.. This has been a challenging week. I wonder what is in store for us in tomorrow’s Prize?
AP@20 Thanks
A crossword for which Chambers dictionary is no help. Not happy.
Very tricky with several unheard-ofs, and I had to resort to some cheating.
Like others I was puzzled by “sections” in LATE LATIN. AP’s suggestion @20 seems to be the most convincing so far — it means the individual letters of Rio being removed rather than the word as such.
I think the idea of “Early Porsche development” is that the car was designed by Ferdinand Porsche and his team (according to Wikipedia), rather than the current relationship between VW and Porsche.
scchua, RATHOLE is actually an across clue — does that make any difference to whether B is the “cover” of Bath?
Many thanks both.
Enjoyable. Very little went in on the first pass, and then everything else on the second, which was an odd experience.
One person’s popular culture is another’s obscurity, but I am surprised at how many are unfamiliar with ROFLMAO. I am over sixty, and I feel like my generation invented that abbreviation as well as its various cousins?
Thanks to all who have pointed out my slips. I have tweaked the blog accordingly.
I had no trouble with ROFLMAO, but I’ve never before encountered a LAVABO.
At least I was able to complete this puzzle, unlike the 3 previous this week!
Thanks to Yank for a hugely challenging and enjoyable puzzle. Like others I had a couple that I needed to check, but it’s always good to expand the vocabulary.
Thx also to scchua for the blog.
bodycheetah@21 – I just assumed it would be “sirbed”, didn’t even look it up.
Really enjoyed this – thanks to Yank and scchua.
never heard of stylet, lawfare, e-wallet or Angus Young.
American note #1 I don’t think “java” for “coffee” has been used in my lifetime. It exists in books.
American note #2, Today, June 19, is Juneteenth, our newest Federal holiday, and a good ‘un too.. President Lincoln freed all slaves in Confederate states by the Emancipation Proclamation on January 1, 1863. But Texas didn’t get the word until the war was over and a union general marched into Galveston and enforced it.
One that seemed to get easier as it went on. Couldn’t parse STYLET and inevitably I put in the alternate spelling.
Liked RATHOLE and VW BUG
Thanks Yank and scchua
Lots of contemporary references, which I applaud. Some of the negative comments say more about the complainants eg I got ROLFLMAO pretty quickly and I’m not Gen Z, I’m 68
Thanks Yank and scchua
I enjoyed that. I’m glad to see another couple of people assumed “sirbed” and thanks to sschua for parsing de-bris.
I would say it’s nice to see some modern references in the crossword, but AC/DC were already a massive band when I first saw Angus lead them 45 years ago (Hammersmith Odeon 1980), and I suspect I first saw ROFLMAO on a chat board over 20 years ago, so perhaps they’re rather contemporary for 60-somethings like me.
Note to self. Don’t waste time trying to solve Yank. No joy to be had in clunky clues and esoteric vocab. 🤷♀️
Erm. Biorhythms aren’t circadian, are they? Their cycles are 23, 28 and 33 days; they have no great connection to the daily circadian rhythm. But I may just be clutching at a face-saving straw because I couldn’t figure out that one answer.
Matt Gibson @39
Circadian rhythms are an example of biorhythms. You are thinking of the discredited pseudoscience theory. See here.
V@34 “But you can’t take your eyes off her, get another cup of java
It’s just the way she pours it for you, joking with the customers”
Tom Waits, “Invitation to the blues” from the classic Small Change album
A bad week for me…
Thanks both…
First encountered LAVABO sometime before French O-level (it is French for washbasin), and I remember I was surprised because it looked decidedly un-French (and that’s because it’s Latin, for “I will wash”). In any case, it helped me get started here. Interestingly, a total of 5 answers ended with O today.
Thanks for the blog , pretty good and original in parts , the ursine Peruvian was less than happy with RHINO . My weekly minutes are up , reset tomorrow .
^ also the programming language and its associated logo
Everyone seems to have had different gaps. I hadn’t heard of STYLET or LATE LATIN and had forgotten the term for genital mutilation. I struggled for so long in the North East but when it fell, it happened quickly. No complaints, I feel the week has beaten me up. I echo Terry’s experience @2 of missing easier clues when I’m struggling.
I liked BEAN SALAD, VW BUG, RATHOLE and CIRCA and agree it’s good to see some marginally more contemporary references
Thanks Yank and scchua
Valentine@34. The last time I remember JAVA for coffee being used was in Dead Men Don’t Wear Plaid, where Steve Martin mixes a cup of his “famous java” for Burt Lancaster, just before he’s shot in the arm and has to get Rachel Ward to suck yet another bullet out (a trick she learned at summer camp). Great movie… ROFLMAO indeed.
One of Yank’s best ones – thanks! But oh, I thought 4A was crying for a Monty Hall problem reference!
Thanks Yank for an amusing challenge. This took me two sittings to complete and I certainly had a few parsing gaps but I thought it was worthwhile because of clues like LAVABO, WEBMASTER, SWINGER, INSTAGRAM, CHILL, and APOLOGIST. Thanks scchua for the blog.
Thanks both and the Gunga Din award goes to all this week’s bloggers. (And the Pére Thumper award to the setters? Near enough.)
I don’t mind an obscurity (LATE LATIN. -BRIS, ROFLMAO, STYLET) – I’m open to learning new words as an aspect of the pleasures of cryptics. But I do mind being asked first to conjure words on the basis of a watery definition and then being asked to manipulate them (Webster (‘wordsmith’), bionic (‘having special powers’ (although this I (almost) could live with), Bath (‘spa location’), aspirated (‘breathily said’), Churchill (‘prime minister’), chemist (‘drug dealer’ (but see ‘bionic’)) and the gob-smacking circadian (5/9ths etc…).
I know, I know – it’s a crossword and should generate ought but gratitude for the distraction. But Bilbo (‘What have I got in my pocket?…) clues are too easy for the setter. Here endeth the annual rant.
HarveyManfrengensen@48: Monty Hall?…..
[Rant was prompted by Martin’s@46 reference to ‘genital mutilation’ which chimed with me – but where to go to do anything about it? (off-topic – hands up)]
I liked this one! DEBRIS made me chuckle, and RHINO had a neat surface. Thanks to the setter and blogger, it was good fun.
NW intractable, plus 15a DEBRIS — dnf. NE also tough, but eventually fell. Kicking myself about 1a LAVABO, which I know. Most of the others well out of reach, so glad I didn’t continue wrestling
Favourites 10a IONIC (memories of the Six Million Dollar Man), 5d CHILL (surface, ouch!), 6d DO-NOTHING (“knight errant”), 19d SQUASH (fun)
Alphalpha@50 “Pick a door”, referring to the Monty Hall problem. Hint: you should always switch your choice
Thanks for a great puzzle and blog. Off to lick my wounds…
Too hard for me. Failed utterly on the NE corner. Ah well, next week is another week. Still I have learned another piece of text speak in ROFLMAO.
Thanks Mig@52
Thanks both,
I knew it as ROTFLMAO. T for ‘the’. In newsgroups, where these things circulated, even the initial letters of definite and indefinite articles tended to be included, IIRC.
I detect a theme: chemise, debris, trousseau, gelato,picador, lavabo are all from Romance languages, i.e. very very late Latin. plus circa.