ACROSS
 7. Q→D, QUALITY = DUALITY <two-facedness>
 9. LIE outside MEAD = LIMEADE <non-alcoholic drink>
11. QUE (IS after BECO_) = QUEBECOIS <Canadian>
12. SOT* IC = STOIC <unemotional>
13. ALTO + G ETHER = ALTOGETHER <in unison>
15. <detect> ESPY = ESP + _Y
17. EXTRA JULY outside (DI + CIA + L) = EXTRAJUDICIALLY <without following legal procedures>
20. NO _O _K = NOOK <secluded corner>
21. <flyer> BUDGERIGAR = BUDGE RIG A_ R
24. C + HILL = CHILL <cold weather>
25. (WHY I GET TO)* = EIGHTY-TWO <deuce with some scores?>
27. (TIN CANS)* = STANNIC <containing tin>
28. LOO'S EST = LOOSEST <least strict>

DOWN
 1. <enough> ADEQUATE = AD + EQUATE
 2. AREN'T after P = PARENT <Mama?>
 3. <arsonist> PYRO = (.p)PY RO(b.)
 4. B LISTERIN[-e] G = BLISTERING <skin irritation>
 5. CAROUSE + L = CAROUSEL <merry-go-round>
 6. <good> PEACHY = ACHY after PE
 8. I (_E inside DOG + RAM) = IDEOGRAM <emoji?>
10. <pal> MUSH <sentimentality>
14. TRUCE outside UNCLE* = TRUCULENCE <stubbornness>
16. BLOTTIER* = LIBRETTO <book>
18. R inside TOPICAL = TROPICAL <sort of storm>
19. YOUTH outside ARM = YARMOUTH <Norfolk town>
20. NICE ST = NICEST <most pleasant>
22. <almost go out> GUTTER = G_ STATE
23. <dessert> FLAN = FLAN[-ders]
26. <chutzpah> GALL = _G ALL