Very enjoyable solve from Phssthpok!
Not too hard, but a few solutions had me thinking for a while before they fell into place. The two long anagrams at 4 and 9 down certainly helped speed things up (and great anagrams at that!) Some of my favourites today include 9d, 15d, 18a and 27a. Many thanks to Phssthpok.

ACROSS
1. Article following church doctrine describes the heavens (8)
CERULEAN
AN (article) following CE (church) + RULE (doctrine)
5. Spots announcement of contract (6)
FLECKS
“FLEX” (contract, “announcement of”)
10. Aesop cooked up a vegetable broth (3-4)
PEA-SOUP
11. Endlessly revere everybody like Nelson (7)
ADMIRAL
(ADMIR[e] (revere) + AL[l] (everybody)) (endlessly)
12. Promote nurse and get a pay increase (5)
RAISE
13. Spreading out old butterflies (9)
EXTENSION
EX (old) + TENSION (butterflies)
14. Face defeat in struggle to get rid of stimulant (12)
DECAFFEINATE
(FACE DEFEAT IN)* (*struggle)
18. Bore crowd with this red composition (7,5)
STUFFED SHIRT
STUFF (crowd) with (THIS RED)*(*composition)
21. Relax because solvers and compilers get on (2,3,4)
AS YOU WERE
AS (because) + YOU (solvers) and WE (compilers) get RE (on)
23. Frozen acceleration due to gravity spike (5)
GLACE
G (acceleration due to gravity) + LACE (spike)
24. Pilot goes through hill following acceleration (7)
AVIATOR
VIA (goes through) + TOR (hill) following A (acceleration)
25. Free to air (7)
RELEASE
26. No end to oriental festival (6)
EASTER
EASTER[n] (oriental, no end to)
27. Shuffle the odds in hoaxer’s card game (8)
CHARADES
(H[o]A[x]E[r]S (the odds in) + CARD)* (*shuffle)
DOWN
1. They add flavour to hops (6)
CAPERS
2. Losing her head, floozy that is employee of the Rolling Stones, perhaps (6)
ROADIE
[b]ROAD (floozy, losing her head) + IE (that is)
3. Some folders are found in tea after teabag malfunction (5-4)
LOOSE-LEAF
4. Arsenal players finally papped tearing up stairs (14)
APPLES AND PEARS
(ARSENAL [player]S (finally) PAPPED)* (*tearing up)
6. Rotten apple or other fruit (5)
LEMON
7. Badge I put on after removing one jacket (8)
CARDIGAN
CARD (badge) + I + GA[i]N (put on, after removing one)
8. One who fixes bone fragment (8)
SPLINTER
9. The best people hurl heartfelt oaths (14)
SALT OF THE EARTH
(HEARTFELT OATHS)* (*hurl)
15. Guerrilla is not punctual (9)
IRREGULAR
Double definition
(with an almost-anagram which briefly threw me off)
16. Stunt flight accommodates a flyer (8)
ESCAPADE
ESCAPE (flight) accommodates AD (a flyer)
17. Panel supplies repairs, temporarily (4-4)
JURY-RIGS
JURY (panel) + RIGS (supplies)
19. Extreme characters enter into bewildering gamble (6)
HAZARD
A + Z (extreme characters) enter into HARD (bewildering)
20. Could some astronomers be lecturing about stars? (6)
CELEBS
[astronomer]S BE LEC[turing]< (some, <about)
22. Release topless woman (5)
UNTIE
[a]UNTIE (woman, topless)
Well, I found this hard but did enjoy it, notwithstanding the holdup caused by the wrong enumeration in both 4d and 9d. The FT really needs better checking – something I seem to mention far too often. Ah well, I live in hope.
Same comments as Hovis @1 as to the level of difficulty and the annoying enumeration slip-ups at 4d and 9d. Still, there were some excellent clues, my favourite being SPLINTER, which is not only a double def but arguably a clue as definition too, with a SPLINTER being someone who ‘fixes’ a ‘bone fragment’ in place. I also liked the ‘teabag malfunction’ at 3d, an all too common occurrence.
I saw ‘butterflies’ in the clue for 13a and ADMIRAL at 11a. I’m no entomologist; any more?
Thanks to Phssthpok and Teacow
As with Hovis@1 the issues with 4d and 9d held me up greatly. The crossword itself was terrific, I thought, but …
Thanks for the blog, I agree with WordPlodder about the puzzle and SPLINTER. I could not find any other butterflies.
I see your point about GUERRILLA/IRREGULAR , there is a good clue waiting to be written swapping an L for R.
Roz @4. Fed had the clue “irregular and liberal – mostly irregular and liberal”. The first irregular being the definition and the first liberal being the anagram indicator. Quite neat I thought.
Thanks Hovis , pretty good .
Thanks Phssthpok. I liked AS YOU WERE and the nicely hidden CELEBS, I missed FLECKS and JURY-RIGS, and I was delayed a bit by the enumeration mistakes. My guessing was better than my parsing today so thanks Teacow for the blog.
Why no word breakdown indicated for 4 and 9 down?!
I am a new solver and this one the me for a terrible poop. With the one possible benefit that it used up all my commuting time on the bus with thinking that I am an idiot. Which I probably am.
I didn’t mean what I wrote! Not pxxp but loop. Apologies!
Perhaps I’m being unreasonable but can we have some proper subbing at the FT please?
How much did I enjoy solving this? See also the answer to “But apart from that Mrs Lincoln, how did you enjoy the play?”
I don’t understand 17dn. What does rigging a jury have to with temporary repairs?
Dieter@12: “Jury-rigged” appears to be the main surviving compound of the old adjective “jury”, meaning “for temporary use”. This appears to be derived from the French “jour” (day), and unrelated to the legal term.
Thanks Phssthpok and Teacow
Another late entry and found it a good challenge, further challenged by the enumeration – in some puzzles that is standard practice I think – to not break down into individual word lengths. Anyhow, it only added time to the solve and didn’t prevent it.
Some nice clues throughout with my favourites including AS YOU WERE, LOOSE LEAF (for the surface) and JURY RIGS. Is a clue like LOOSE LEAF more like a definition with a cryptic word play ?
Finished with CELEBS (caught up with the other sort of stars for too long), APPLES AND PEARS (cos my Cockney rhyming slang isn’t as good as it could be) and AS YOU WERE (tricky).