ACROSS
 1. ←MAD← SELFISH = DAMSELFISH <swimmer>
 8. <fiancé> INTENDED = _N_ inside IT ENDED
 9. C_ HIP = CHIP <piece of potato>
10. (RN + THE ISLAND)* = HINTERLANDS <backwaters>
12. <means of fixing> STAPLE = STALE outside P
14. <past> BEYOND = BEND outside Y_ O_
15. P EASE MEN inside APT = APPEASEMENT <accommodation>
17. <stressed> TAUT = "TAUGHT"
18. <wrestler> LUCHADOR = (LUDO + R) outside CHA

DOWN
 2. AN _NE_ HATH A WAY = ANNE HATHAWAY <better half of Shakespeare>
 3. <inflexible> STERN <part of boat>
 4. LD outside A_ = LAD <young man>
 5. <impossible to remove> INDELIBLE = IN D ELIGIBLE - GI
 6. HACK (_E in NY) = HACKNEY <borough>
 7. FIR STATIONS outside N = FIRST NATIONS <indigenous groups>
11. <stared at> EYEBALLED = "I + BAWLED"
13. <famous singer> POP STAR = POP + S + TAR
16. <correspondence> E-MAIL = ←(.r)LIAME(n.)←
19. <prompt> CUE = "QUEUE"