ACROSS
 9. <script> OGHAM = O_ G HAM
10. A NATION outside I'M = ANIMATION <vivacity>
11. (NORSE CLUE)* = ENCLOSURE <pen>
12. <origins> ETYMA = _E_ T_Y _M_A
13. (MOTHER'S)* = THERMOS <drinks kept in here>
15. INTO IT outside R = INTROIT <service entrance>
17. <festive song> CAROL OF THE BELLS = CA (LOFT HEBE inside ROLLS)
20. RUBENS* outside A = SUNBEAR <Southeast Asian mammal>
21. <cried> BLEATED = AT inside BLEED
22. <maintain subscription to> RENEW = ←WIENER - I←
24. SHE + PHDS outside ER = SHEPHERDS <crooked men>
26. <celebration of St Stephen> BOXING DAY = →"DOXXING BAY"←
27. <what turns> LATHE = HE after LAT

DOWN
 1. <housekeeper> DOMESTIC = DOME + STIC[-k]
 2. CHIC KEN RUN = CHICKEN RUN <stop-motion film>
 3. A MMO = AMMO <rounds>
 4. A QUI inside MS = MAQUIS <Resistance fighters>
 5. <treacherous> VIPERISH = VI PERISH
 6. <unfortunate> LAMENTABLE = LA_ MEN + TABLE
 7. _L IVY = LIVY <Roman historian>
 8. <child> INFANT = NAIF* + NT
14. MULL + EDWIN _E = MULLED WINE <drink>
16. <eliminate> OBLITERATE = ←BO← + L + ITERATE
18. <warm place> FIRESIDE = F_ I_ RESIDE
19. <avoid> SIDESTEP = S DESPITE*
20. <flasher> STROBE = ST + ROBE
21. "BUY BY" = BYE-BYE <so long>
23. <clothes retailer> NEXT = X inside NET
25. <religious> HOLY = "HOLEY"