ACROSS
 6. ONE FORT HERO AD = ONE FOR THE ROAD <Pinter play>
 9. CH (LSE inside EA) = CHELSEA <football club>
10. <smaller map> INSET = INSERT - R
11. <choose to ignore> WAIVE = "WAVE"
12. <betray> = CHE (A TON)
14. <sheepdog> SHELTIE = SHE L + TIE
16. ROB inside PE = PROBE <investigation>
17. L_ inside FAIR = FLAIR <panache>
19. <hunch> INKLING = TINKLING - T
21. (CERTAIN ANIMAL)* = LATIN-AMERICAN <from Mexico?>

DOWN
 1. <neckwear> TORC = T_ O_ R_ C_
 2. ←(.s)EFIRE NET(h.)← = TENERIFE <island>
 3. <mess up> TOUSLE = SEOUL* after T
 4. <corrupt> DEFILE = _D + (E FILE)
 5. ←S + DOG← = GODS <theatre's highest seats>
 7. <80s attitude> Thatcherism = THAT CHER IS M_
 8. (.e)DE TEN TE(r.) = DETENTE <diplomatic thaw>
11. <fondly reminiscing> WISTFUL = W I STFU L_
13. (I COPE)* inside WET* = TWO-PIECE <suit>
15. <despot> TYRANT = RANT after TY
16. P_ A_ KORMA - M = PAKORA <fried appetiser>
18. <pot grower> ANTE {thing that increases a pot of money}
20. <fellow> GENT = [-a]GENT[-s]