1 Prepares the telescope to find a volcano (5,2,6)

 9 One who drinks like a fish (salmon), immersed in every vice, essentially (9)

10 His or her or his and her—not here, I hear (5)

11 Pierre’s here with half-clever one that hangs around the house in wintertime? (6)

12 Battalions of babies? (8)

14 Lumps in egg-nuts stew (7)

15 Singer-actress snatching back tot’s cheese (7)

17 Country enthusiast, on the rebound, lives near Iowa (7)

19 Aides originating at university near Paris, perhaps! (2,5)

22 Between a rock and a hard place in Afghanistan (8)

24 Grove conceals back of your body (6)

26 Donne is obscure? Exceedingly (2,3)

27 Plagiarized Broadway musical returns after cutoff, missing first part (9)

28 Declaration—for example, “We unite” (13)

 1 Monarch of comfy shoes? (That’s sarcastic) (7)

 2 Appellate courts often confiscate source of some auto accessories (9)

 3 Legendary archer, say (4)

 4 Expert: engineer, not catcher (10)

 5 Texas regressively enters age of surplus (5)

 6 Chose participants in returning cadet celebration (7)

 7 Mister Softee’s primary appeal (7)

 8 Head of ministry to straighten out evil (6)

13 Mixed-case writing in ancient Rome restricted Occitan’s initial expansion (10)

16 Surveillance of sea pigeon in a storm (9)

17 Engaged teaching assistant with a bit of experience in ascendant musical genre (5,2)

18 Ron gets lost around 11:00 in Montreal—this could be positive or negative (7)

20 Broadcast network invested in the second New Testament available for reading (2,5)

21 Drunk dries up? (6)

23 Initially, awful, ugly din is organized sound (5)

25 Frost poem (4)
 

ACROSS 1 THE(NC)E 4 CAR PAL 9 INFER + I + OR 10 “aye, cutest” 12 IN + EPT (pet anag.) 13 PA + R + RICIDE (I cried anag.) 14 TO + AD (initial letters) + IED 16 NOS + TRIL[lion] 17 co[a]ching anag. 19 “I, whole” 21 A + B(SENT)EES 22 BO(FF)O 23 2 defs. 24 hidden 25 anag. 26 AN ODE + S
 
DOWN 1 TAF + FETA (fat rev.) 2 rev. hidden 3 viler anag. 5 “[M]ac oui yes” 6 P(REM)IER 7 pun 8 anag. 11 FRANKEN STEIN 15 [v]INCENT + I’VE 18 ONSH + OR + E (nosh anag.) 20 OFF + ICE + S 22 B(I[m]P)ED