Fastest Indy solve of the year so far for me, 13 mins. Unusually got many answers first from the definitions. Some excellent clues as always from Dac.

* = anagram

ACROSS

1 KIRS CH (irks)* church leaders = 1st 2 letters. It’s a brandy.

4 Robert BROWNING Excellent surface.

10 NO M (I N) ATES ref Billy no mates.

12 A-STREAM (as a term)* Favourite clue - a great &lit “Pupils likely to achieve highly as a term develops”

14 C LEAR SIGHTED “Cited”

17 DEMONSTRATOR Though it looks like there’s some wordplay, it’s a double definition.

20 DELI BES(t) (idle)* George Best ref musical score i.e. a composer. ‘briefly’ means ‘omit last letter’

22 TAG LINE (e.g. Latin)*

23 LINDA Cunningly hidden - indicated by ‘clothes’

DOWN

1 KEN DAL(e)

3 CANN(EL)LINI BEANS El = the Spanish in (nine cannibals)*

6 WAITING FOR GO (DO) T Samuel Beckett play do = party forgot = neglected circulate = go outside in container and contents

9 S (society) T (A MP) ACT Not sure if the surface is in line with the history of that tax in America.

15 STAR T OUT Another top drawer clue.

17 (D)ID(D)LER “Cheat and wastrel having hat encrusted with diamonds”. A little elaborate, this. I think it means the wastrel = idler has a hat of diamonds (D, from cards) - this is a down clue and also a second D included i.e. encrusted. Definition = cheat

(Testy’s note in comment 1 below explains this correctly, I’d say)

18 PI G OUT Pi = very good (from pious) Taste at Maxim’s = taste in French = gout.

21 SUPPE pp for it in suite 19th century composer.

This was tough, and certainly I wouldn’t have been able to solve it on the train! However, I’m between jobs at the moment so I was able to attack it with Chambers and Bradfords (although 19D required TEA as well). The theme appears to be phrases that mean the same as 11,1 but only in a tongue-in-cheek way.

Across
1 MIST,AKE (”ache”) - second half of the thematic phrase which you need to solve 3 or 4 other clues. I’d solved half the puzzle before I got this.
5 COVE,RUP(ert)
10 ROUTINEER - “route in ear”. New word for me, meaning a person who follows a routine.
11 DELIBERATE - easy double definition, but I didn’t get it for ages.
12,14 SLIP OF THE TONGUE (hot soup gentle if)* - I worked this out before getting 1A; in fact it led me to the answer.
18 A,SEPT,ICISED=(is dice)*
21,27 JU(ST,TES=set rev,TIN)G
22 DEPORT,MEN,T - I’m not too keen on model=T (as in the old Ford), but a lot of setters use it lately.
25 INCUNABLE - INCURABLE with the middle letter changed. Another new word - I’ve heard of incunabula (books printed before 1501) but didn’t know it could be anglicised.

Down
1 MA,LADY - took me ages to work out the wordplay. At first I thought LAD in MAY, and where’s the aristocrat?
3 ANNE BRONTE (near bent on)*
4 (t)ERROR
6 VEIL - I think this refers to Hamlet’s “Get thee to a nunnery!” speech to Ophelia.
7 RHEOLOGY - theology with change of first letter.
13 GOOD,STRAIN
15 TUC(cut rev),KERB,AG
16 BAN,JOIST - I’ve seen a very similar clue somewhere else recently.
17 BE(DSO)CKS
19 ZEN,ANA - an Indian or Iranian version of a harem. I don’t think I’d have got it without TEA.
20 A(TWO)RK
24 ANTI - “auntie”. I think “maybe related” makes this work as a homophone, as it gets round the “not in my accent” criticism.