ACROSS
9. ELECT _RA_ = ELECTRA <Sophocles play>
10. S_H ON outside W MA = SHOWMAN <impresario>
11. (...l)IN TEL(l...) = INTEL <secrets>
12. <kinswoman> GREAT-AUNT = RAGE* TAUNT
13. <fun> ENJOYMENT = MONEY* outside J + _E _N _T
15. <sort of setter> IRISH = ←_H_ SIRI←
16. <JM Barrie play> QUALITY STREET = QUAYS outside LIT + TREE _T
20. <longed> PINED = _N inside PIED
21. AA outside (A SINGLE)* = ANALGESIA <lack of sensitivity>
23. Y S_ inside POLEMIC = POLYSEMIC <with multiple interpretations>
24. _N_ (MB inside II) = NIMBI <clouds>
26. P STAG inside U_E_ = UPSTAGE <to steal the show>
27. THE outside E AT _R = THEATRE <playhouse>

DOWN
1. <local> DENIZEN = DEN outside ←ZINE←
2. <musical> RENT <in two parts>
3. <influential> AT PLAY = A + (TOP - O) LAY
4. <most moth-eaten> MANGIEST = MAT outside (DESIGN - D)*
5. <declare> ASSERT = "A CERT"
6. TOOT H IE R = TOOTHIER <having more prominent dentures>
7. I M_M + INSURES* = IMMUNISERS <items providing pre-emptive protection>
8. <short piece of music> SNATCH = S NATCH
14. <hack writing> JOURNALESE = JOULES outside RNA + E
17. <one directing Jack> LODESTAR = LEOTARDS*
18. TOCCATAS* = STACCATO <with short, detached notes>
19. <afternoon performance> MATINEE = IN inside MATE E
20. OPS inside PUP = POPS UP <makes an unexpected appearance>
21. <hosts> ARMIES = ARIES outside M
22. <they're shooting> GUNMEN = G UN M_E + N
25. <self-referential> META = (...o)ME TA(l...)