ACROSS
 1. ←ASSAM← CH USE TT = MASSACHUSETT <American>
 8. <seaside attraction> PIER = IE inside PR
 9. DE_ LIBERATE = DELIBERATE <planned>
10. <beat> RHYTHM = _R _H _Y_ T_ _H _M
11. NICE* P + HER = ENCIPHER <disguise>
13. (MAN TRIES)* outside X = AXMINSTER <carpet>
15. I + R_ ON = IRON <smoother>
17. F LOG = FLOG <to beat>
18. (DOILY GRAN)* = ADORINGLY <with love>
20. PARA + _S inside LYE = PARALYSE <demobilise?>
22. <swallow> ACCEPT = CEP inside ACT
24. <lusty> LIBIDINOUS = LIB IOUS outside DIN
26. <splinter group> SECT = SEC T_
27. <very small> TEENSY-WEENSY = TEENS + YY outisde WEENS

DOWN
 1. <excellence> MERIT = ER inside MIT
 2. I'M inside SEDENTARY = SEDIMENTARY <sort of rock>
 3. [-m]AILMEN T_ = AILMENT <complaint>
 4. ←BO + H← = HOB <stovetop>
 5. <little kid> STRIPLING = _S TRIPLING
 6. <name> TITLE = TIT L_E
 7. <cocktail> HIGHBALL = BALL after "HI"
12. CARD SNAIL* + IN = CARDINAL SIN <sloth?>
14. MIG RATION = MIGRATION <movement of people>
16. _OL_ _YM_ + PICS = OLYMPICS <sporting event>
19. <repetitive> ONE-NOTE = ←(.v)E-TONE NO(c.)←
21. + A L, I'VE = ALIVE <not dead yet>
23. CU SHY = CUSHY <not needing much work>
25. <climber> IVY = "IV"