Across:
8 Shots (= anagram indicator) of pros (of pros = PROOFS) in early editions of the volume (PROOFS),
9 Cape Horn (Cape Horn) showing off (= anagram indicator) (Cape Horn = CHAPERON) guard of honour (CHAPERON),
10 Pesky insect feeding on sweet stuff (GNAT) along the sides of tapioca pudding (along the sides of ‘TApioca puddiNG’ = tang) sent back (= reverse indicator) (tang = GNAT),
11 Drink (TOM COLLINS) produced by writer (tome) mostly (e) (‘tome’ without ‘e’ = TOM) in the dictionary business (COLLINS) (TOM COLLINS),
12 Look (peek) up (= reversal indicator) (peek = KEEP-) English (-E-) Royal (-R) (KEEPER) in The Guardian (the guardian = KEEPER),
14 To sail over (LEAP- over) river (-R-) in heavy mist (-F-OG) (LEAPFROG) is child’s play if you can get over it (LEAPFROG),
15 For the most part (s), 25 across (‘corrects’ without ‘s’ = CORRECT-) and writer (-ED) associated with 8 across (‘proofs’ = PROOFS) (CORRECTED PROOFS) worked in the bookmaking industry (CORRECTED PROOFS),
18 Greatly (greatly) shaken (= anagram indicator) (greatly = LET-ARGY) consuming heroin (-H-) (LETHARGY) as it saps the energy (LETHARGY)
20 Fraud (MISUSE) by mysterious missing Tory (‘mysterious’ missing ‘Tory’ = mseius = MISUSE),
22 A sequence of bloomers (DAISY CHAIN) produced by stand (podium = DAIS-) at Railway End (‘railwaY’ end = -Y) sounds (= homophone indicator) serious (‘serious’ = ‘series’ = CHAIN) (DAISY CHAIN),
24 Clients out of nickel, steel (‘clients’ out of ‘nickel, steel’ = kele = LEEK) and veggie? (LEEK),
25 Points out mistakes (CORRECTS) to college (C-) rector’s (rectors) boss (= anagram indicator) (rectors = -ORRECTS) (CORRECTS),
26 Crops up (OCCURS) with wild (= anagram indicator) crocus (crocus = OCCURS).
Down:
1 Second hole (second ‘hOle’ = O-) is for the golfers testing their drivers (-RANGE) (ORANGE) by lodge (ORANGE Lodge),
2 Throw light on (throw light on = SORT) up (= reverse indicator) in Montrose (in ‘monTROSe’ = tros = SORT),
3 Recites (recites) misprint (= anagram indicator) (recites = ES-TERIC) about old (-O-) (ESOTERIC) secret (ESOTERIC),
4 Smart Alec misses alert (‘smart alec’ misses ‘alert’ = smac = SCAM) of fraud (SCAM),
5 Temple (PAGODA) sets up (= reverse indicator) a (-A) greyhound (dog = -GOD-) agency (Associated Press = AP = PA-) (PAGODA),
6 Stomach (BELLY-) for awful theatrical productions (-FLOPS) (BELLY-FLOPS) in some dives (BELLY-FLOPS),
7 The Leaving (GOING OFF) – of course, it’s nearly past its sell-by-date (of course/meal, it’s nearly past its sell-by-date = GOING OFF)
13 Curses harp (curses harp) playing (= anagram indicator) (curses harp = PURCHASERS) by those taking stock (PURCHASERS),
14 Cautious local (‘cautious’ locally = LEERY) is running through Cork (River LEE-) from railway (-R-) yard (-Y) (LEERY),
16 Tour manager (tour OPERATOR) with Carmen (Georges Bizet’s Carmen = OPERA-) is upset (= reverse indicator) going to rack and ruin (rot = -TOR) (OPERATOR),
17 Peppers (PIMENTOS) park (P-) with one (-I-) type of Jamaican folk music (-MENTOS) (PIMENTOS),
19 Concerto Grosso lacks songster (‘concerto grosso’ lacks ‘songster’ = cocoro = ROCOCO) – the one that’s theatrically ornate at the end of the Baroque movement (ROCOCO),
21 Paid off – disappears (‘paid’ off ‘disappears’ = spears = SPEARS) with old weapons (SPEARS),
23 House sparrow trapped (‘housE SPArrow trapped = espa) flying around (= reverse indicator) (espa = APSE) in the church (APSE),
24 Some upsetting (= reverse indicator) house calls (some ‘housE CALls’ = ecal = LACE) in Chantilly (Chantilly lace = LACE).