Fifteensquared

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.