Myrtilus stopped by the forum to apologise for delaying some solvers rather longer than intended with this one. Apology unnecessary, of course. If it didn't hurt, what would be the point? Which sounds a bit like something the big sister of 26a would say.
As it happens, I didn't spend too long on this because I ground to a shuddering halt with nearly half done, knew I was stuck and resorted to aids to get myself going again.
I needed to hit the books a second time to finish the puzzle off with the two 13s. I would never have got these without help. Much of the rest was very doable, though, and with the sort of eclectic mixture of references I enjoy most in a TLS puzzle.
I have an error, according to the Club site, but I still haven't sorted it out. Everything appears to parse, so either it's a typo I just can't see or I've got completely the wrong end of the stick on something. I'm sure you'll let me know!***
*** thanks to the sharp eyes of JerryW for spotting that in the grid seen below I had typed DORCAS as 'DORCUS'. I'll leave the slip for posterity.
Anyway ... the game is seven card stud:
   | Across 1 LA(WREN)CE for the first part of the top-line pun, completed by: 6 (b)OLIVIA, reference is Twelfth Night 9 DORCAS was raised from the dead by St Peter (Acts), and Dorcas Lane is the post mistress in the Candleford books of Flora Thompson 10 TRINCULO— (IN COURT)* circling L, for the jester in The Tempest 12 ARCHER— I've a feeling the former MP for Louth would rather like the "ex-con" epithet 13 DEL,TA— research needed on my part to discover that delta, usually as Δ, typically denotes a value of incrementation or change. Steady on, Myrtilus — how's an arts grad s'posed to know that? 14 DEATH,T,RAP— never heard of it, but Ira Levin's 1978 play seems to be very much an American Mousetrap, holding the record as the "longest running comedy-thriller on Broadway", though I'm not sure how many comedy-thrillers make it to Broadway 23 DAUGHTER is a reversed RED around AUGHT 24 LADY ANNA— canny stuff. It's LAD (Fellow) preceding a reversal of 'ANNAY, that 'ero being Richard Hannay. Mr Standfast is the 3rd of Buchan's Hannay novels. Trollope wrote Lady Anna to pass the time while en route to Australia 25 B,'UMBLE 26 STELLA, Blanche's kid sister in Streetcar, here a soundalike of 'stellar' 27 EARN (get) + SHAW (:sure), this being Catherine of Wuthering Heights. Heathcliff is referred to as a gypsy a few times in the book Down 2 A(POST)LE— I love this definition 4 NESBI,T— Ibsen going up, then 'there' without the 'here' giving T. Sweet 5 ENTENTE CORDIALE is an anagram of "reacted to nine" followed by the French article LE 6 OXIDANTS— I(one)+DANT 7 V,OUCH,ER(Her Maj) 8 APOCRYPHA— (APPROACH,Y)* 13 DECAPOLIS— my other known unknown, this being the "ten cities on the eastern frontier of the Roman Empire in the southeastern Levant". Parsed as SPACED reversed around (OIL)* 15 THE(CHI)MES— A Dickens short story set at new year 20 THE FLEA— super cryptic def. for John Donne's unforgettable poem (lines) occasioned by a double flea-bite, the hoper being the flea 21 DUN,BAR— Paul Laurence Dunbar was the lyricist of the epochal musical In Dahomey |