A rather chewy offering from Hippogryph this morning. For this solver, at least.
Abbreviations
cd cryptic definition
dd double definition
cad clue as definition
(xxxx)* anagram
anagrind = anagram indicator
[x] letter(s) removed
definitions are underlined
Across
1 Attractive employment opportunity in testicular enhancement surgery?
PLUM JOB
Let’s get the funniest clue out of the way first, shall we? A dd cum cd.
5 Burglar in Shoreditch that’s likely to end up in hot water
TEA LEAF
Another double definition with the second one cryptic or whimsical. TEA LEAF is Cockney rhyming slang for thief.
9 Roaming Epsom Downs
MOPES
(EPSOM)* with ‘roaming’ as the anagrind.
10 Matilda reworked by an Adriatic resident
DALMATIAN
A charade of (MATILDA)* and AN. The anagrind is ‘reworked’.
11 Touchstone‘s requirement to be inspired by working titles
LITMUS TEST
An insertion of MUST in (TITLES)* The insertion indicator is ‘inspired by’ and the anagrind is ‘working’.
12 What could follow on from club‘s spinning difficulties
SODA
A reversal (‘spinning’) of ADOS. CLUB SODA is what Americans call soda water.
14 A flirty swot developed into international chart topper
TAYLOR SWIFT
(A FLIRTY SWOT)* with ‘developed’ as the anagrind.
18 Perhaps chicken crosses major road to join vulture
LAMMERGEYER
An insertion of M for motorway and MERGE in LAYER. The insertion indicator is ‘crosses’. Great surface, obscure bird; but I’ll take the Obligatory Pierre Bird Link even though this is a species new to me. It’s known in English as the Bearded Vulture. LÄMMERGEIER (sic) in German means ‘lamb vulture’, based on the old but mistaken belief that the bird would prey on lambs. More accurate is its name in Spanish, Quebrantahuesos, meaning ‘bone breaker’. The vast majority of its diet comes from carrion bones, which it drops to break and then ingests. It has a unique avian digestive system with extremely acid stomach juices.
21 Champ in essentially atrocious shape
CHEW
A charade of C for the middle letter of atroCious and HEW.
22 Die-cast ring entrepreneur imports acid
ASTRINGENT
Hidden in Die-cAST RING ENTrepreneur.
25 Barrier erected as a result of Spooner’s fight in Northern Scotland
BRICK WALL
A Spoonerism of WICK BRAWL.
26 Heard why seaweed from the East is rich in essential element
IRONY
A reversal (‘from the East, since it’s an across clue) of Y and NORI. Rich in iron is IRONY in the same way as an octopus is ARMY.
27 Setter is regrettably backing square sausages
SALAMIS
A reversal of I’M ALAS, followed by S.
28 Government trimmed part of the army
REGIMEN
REGIMEN[T]
Down
1 Afternoon retreats in mountain spot
PIMPLE
An insertion of PM reversed in PILE. The insertion indicator is ‘in’. ‘I’ve got a pile/mountain of papers to mark this evening.’
2 Elevated feeling of empathy is difficult to control
UPPITY
A charade of UP and PITY.
3 Liberal judge hates Euro-American national park
JOSHUA TREE
(J HATES EURO)* with ‘liberal’ as the anagrind. The Joshua Tree National Park is about 130 miles east of Los Angeles.
4 Item to assist washing behind ears trialled initially under offer
BIDET
A charade of BID and ET for the initial letters of ‘ears’ and ‘trialled’.
5 Brief violent disturbance in match report? That is probably exaggerated
TALL STORY
An insertion of STOR[M] in TALLY. The insertion indicator is ‘in’.
6 Discovered wildlife trip a long way away
AFAR
[S]AFAR[I]
7 Prepared cod pies, eating one from time to time
EPISODIC
An insertion of I in (COD PIES)* The insertion indicator is ‘eating’ and the anagrind is ‘prepared’.
8 Trump’s trousers in English painting?
FINE ARTS
An insertion of IN and E in FARTS. The insertion indicator is ‘trousers’.
13 Separating from Esther? The woman’s away and phoned up during golf!
ESTRANGING
A charade of EST[HER], RANG, IN and G for the phonetic alphabet ‘golf’.
15 It’s your turn, we’re told, to toil endlessly ahead of South Balkans race
YUGOSLAVS
A charade of YUGO (soundalike for ‘you go’, or ‘it’s your turn’), SLAV[E] and S.
16 Site manager detailed ineffective medication
PLACEBOS
A charade of PLACE and BOS[S]
17 Academician put in danger rings London college
IMPERIAL
An insertion of A in IMPERIL. The insertion indicator is ‘rings’. A for ‘Academician’ will be in dictionaries.
19 Party hire for merchant banks
REFORM
Hidden in hiRE FOR Merchant. REFORM does appear to be for hire if you are rich enough.
20 Ban on sailing vessels turning up and dropping off children is to remain after all
STAY ON
A reversal of NO and YA[CH]TS.
23 Where lurchers rounded, guarding the King?
RULER
Hidden reversed in wheRE LURchers.
24 Read superficially, Jagger’s missing constant “rolling”
SKIM
‘Jagger’s’ is ‘Mick’s’. Remove the C for the physics ‘constant’ for the speed of light, reverse everything, and, as Mick sang, you just might get what you need.
Many thanks to Hippogryph for this morning’s puzzle.

Well, I had CODA for 12(ac), I may be wrong as usual.
I enjoyed this. 18a was new to me but fairly easy to derive by following the instructions in the wordplay.
My top picks are PLUM JOB, TEA LEAF, BRICK WALL, PIMPLE and YUGOSLAVS.
Many thanks to Hippogryph and to Pierre.
Me too, Pierre; in fact, I flunked 12(ac), entering CODA, ( misled by the word CODICIL, an addendum to a Will ).
I fluked LAMMERGEYER, but it was my second attempt, and I still wasn’t convinced. ( Great info, by the way ).
TOUCHSTONE, 11(ac), led me up a Shakespearean blind alley.
Lots to enjoy, ( BIDET: best in show ), but I had a few quibbles, such as the superfluous “opportunity”, in 1(ac); the definition (or not), for IRONY; the pluralisation of FINE ARTS, ( of which painting is but one, “fine art”.)
Sour grapes/gripes from me, no doubt, because I messed up SODA!
It’s a skilful puzzle, very enjoyable.
Thumbs up, Hippo et Pierre
Entertaining puzzle. Lots to amuse including the ‘Wick Brawl’, ‘pile’ for ‘mountain in PIMPLE and the fun surface for 18@ as mentioned above. And IRONY. Thanks Pierre and Hippogryph.
Steady work, although I was misled by trying to make Emmanuel fit the college, even though I knew it wasn’t close to London… I was also slow to see the Wick Brawl, as I only moved the B to begin with… the bird i know better as the Gypaete Barbu, due its bearded appearance, which has been reintroduced into the area of the Alps I’m fortunate to live in. An extraordinarily large wingspan, 3+ metres! Previously hunted to extinction locally, its red(dish) chest feathers (clearly shown in Pierre’s link) were thought to be blood stains. Really amazing sight.
Thanks Hippogryph and Pierre..