As is the case with his Guardian puzzles, Cinephile (aka Araucaria) often includes a thematic element or array in his FT publications. This particular puzzle was made slightly less tractable than usual by the absence - in my edition of the paper at least - of any rubric to denote that the bracketed numbers in several clues were thematic shorthand and not merely misprints (the fact that 25a contained a genuine, but obvious, typo didn’t help in that regard).  However, I soon rumbled 23d (6)=(JUNta), and thereafter the theme (numerics equating to abbreviated names of months) actually helped to accelerate the solving process overall.  So somewhat relieved that, despite an initial minute or so of fear, my blogging debut did not require any black-belt solving skills.

Across
5 om in dingo - the surface reading “eaten by wild dog” reads slightly implausibly, unless you happen to remember Sam Peckinpah’s films perhaps? I think I’m right in saying that Placido Domingo translates into English as Quiet Sunday.
9,10 rig,hat*,sat,rivet - The phrase “Right as a trivet” is new to me, but the wordplay made things straightforward enough
12 JUL,ep - the first of the thematic “monthly” clues. 
21 bide,t - this word is tailor-made for use of the “biding time” mechanism. “In the bathroom” is typical of Araucaria’s laissez-faire definitional canon, but doesn’t strike me as unfair.
23 JAN,i,tress - has anybody ever met a female janitor, or at least one who uses this moniker?
25 cid,e in Inn,CE - my copy had “puib” instead of “pub” in the wordplay, but no harm done.
26 SEP,i,a
27 (use aria)* - one of the clumsier surface readings.
28 MAY,oral

Down
1 APR,i,cot
2 AUG,mentor
6 MAR,i(J)uana
7 NOV,el - maybe it’s just me, but it feels like the use of “railway”=EL is almost as prevalent as the more traditional “railway”=RY these days.
8 OCT,opus
16 a,t,hen,a,(emu)* - I know that The Athenaeum is some kind of venue for the Great and the Good. But (in crossword parlance) my “non U” status precludes any detailed knowledge.  Please feel free to enlighten me, by way of a guest invitation, if you happen to be a member of the club yourself.
18 FEB,rile
22 DEC,or - I sometime wonder how many times a veteran compiler must have had to deal with a common-or-garden, filler word such as this.  I suspect that Cinephile’s answer would be “Too many!”
23 JUN,TA
24 ST in TAY - For some reason the phrase “Succulent way to enter river” put me in mind of medieval ducking stools!

The usual excellent, accessible, entertaining, fare.

Solving time: 19 mins

* = anagram

ACROSS

1 BLOOMS BURY   Not a container and contents!

6 C (A) MP

12 LIST-LESS

21 MAIN STAY    Sea = main also used in Times today.

24 CAT S   The musical

25 NIGHT NIGHT     A contributor to this site nearly gave this away last night under “setters”  “Knights” = chessmen (men on board)

28 S ARK   Channel Island

21 ME THUS ELAH   Hale reversed (also used in Times today)

DOWN

1 BLENCH   Double definition

3 MARCH 1 (start of  month) ONE SS

5 RUSSIANIST  (is anti-USSR)*    Topical

8 PARA SITE

13 THE SOPRANOS  (A person shot)*  &lit  a watcher assures me.

14IM (o)PERATIVE    Definition:  required    No hat = take off first letter (in a down clue)

16 HAM MOCKS

19 BEN GAL

20 STITCH   Double definition

23 UH-UH   Take soldiers (TA) twice out of Utah.    US usage for no (had to verify that)

This wasn’t too tricky but there were a few answers that I don’t fully understand - explanations/corrections welcome.

I was too busy at work yesterday to finish the puzzle, so I completed it when I got home, only to find that my ADSL connection was down. It didn’t come back up until gone midnight, so here I am back at work hoping for a quieter morning to get this done quickly!

Solving time - 10 minutes in odd snatches at work, plus maybe another 10 at home to finish it. There was some dodgy wordplay interspersed with some excellent clues. Gordius is obviously no fan of Jeffrey Archer or the Bushes!

Across
1 TRACTION (into art c)* - nice misleading surface.
5 A,B(US)ED - “us” or “we” for “Guardian” is used quite often by most of the Guardian setters, as is “setter” for I (although not always - see 21ac).
9 RECLINER - “wreck liner”
10 SC,RAWL - SC is short for “scilicet”, Latin for “namely”, or “to wit” as it’s used in 7dn. I don’t think “informal writing” is a good definition though.
14 BALL,O’TRIGGER - I didn’t understand the wordplay at first, but looked up The Rivals by Sheridan and was pleased to see that one of the characters is Sir Lucius O’Trigger. Jeb Bush (Dubya’s brother) was governor of Florida at the time of the disputed presidential election result there.
18 HANDEL’S LARGO (Len’s goal hard)* - took a long time to decipher, even though I was looking for the name of a piece of music from the start.
21 NEW STREET - answer is wordplay for “setter”, Brummie is a Guardian setter, and New Street is a Birmingham railway station. I thought this was a brilliant clue.
24 A,TAXI,A - last one I put in, along with 22dn. Only vehicle I could think of at first to fit ?A?? was CART, then I was looking for ?A?A because of a mistake. Duh!
25 CON(I)FERS
26 SOLD(i)ER - slowed down by putting TRASH in for 22dn at first, which clogged up the whole SW corner till the end.
27 TSIGANES (Sign Teas)*
Down
1 THRACE (the car)* - I thought this was a bit unsatisfactory. It’s sort of supposed to be an anag. &lit clue, but doesn’t work for me.
2 ARCHER - refers to Jeffrey Archer, who was jailed for perjury in 2001, but surely it’s a crossbowman who’d shoot his bolt, not an archer?
3 TAILPLANE - “tale plain” - another one I didn’t like: the wordplay indicates “plain tale”.
4 OPERA GLASSES - why “Stargazers?” - I don’t get it.
6 BACON - nice triple definition. The philosopher is Roger Bacon.
8 DIL(=lid rev),A,TORY
15 IN,GROWING - nice double CD
17 SNOWBALL - not Tony, but Eric. Snowball is one of the pigs in Animal Farm.
19 GIDE,ON - André Gide, Gideon in the Bible.