Across:
8 One of many by Vivaldi (SONATA) produced wince from Isaac Newton (‘wince’ from ‘Isaac Newton’ = saanto = SONATA),
9 Tour manager (tour OPERATOR) with Carmen (Georges Bizet’s Carmen = OPERA-) is upset (= reverse indicator) going to rack and ruin (rot = -TOR) (OPERATOR)
10 Stable type (STUD) of cortisone from discount store (‘cortisone’ from ‘discount store’ = dust = STUD),
11 English (-E-) workers (-MEN-) in nude to (nude to) play (= anagram indicator) (nude to = DENOU-T) (DÉNOUEMENT) the final scene (DÉNOUEMENT),
12 A high-pitched reaction (SCREAM) to last of the reds (last of the ‘redS’ = S-) coming in contact off white? (off-white = -CREAM) (SCREAM),
14 Submissive nature (MEEKNESS) of nemeses (nemeses) working (= anagram indicator) (nemeses = MEE-NESS) over the weekend (‘weeK’ end = -K-) (MEEKNESS)
15 Storage facility (CLOUD) in Switzerland perhaps is timely for the birds (CUCKOO LAND) (CLOUD CUCKOO LAND) or for the dreamers in a fanciful place (CLOUD CUCKOO LAND),
18 Sounds harsh (TUNELESS) for time (T-) at a foreign (‘a’ = -UNE-) takeaway (-LESS) (TUNELESS),
20 Dream (dream = DEAR M-) move (= anagram indicator) to Spain? (-E) (DEAR ME) Oh no! (DEAR ME),
22 Graduate (BA-) from The Palace (-KING) contacts 24 across (‘soda’ = SODA) (BAKING SODA), an agent responsible for The Rising (BAKING SODA),
24 Drink (SODA) served up (= reverse indicator) in Colorado Springs (in ‘colorADO Springs’ = ados = SODA),
25 The most immaculate (CLEANEST) castle (C-) on meadow (-LEA-) with tree house (-NEST) (CLEANEST),
26 Opens 15 across (opens ‘cloud cuckoo land’ = CLOUD-) with foundation creams (foundation creamS’ = -S) (CLOUDS) offering sunblock (CLOUDS).
Down:
1 Steal from Police State (‘steal’ from ‘Police State’ = poicet = POETIC) – there’s a kind of justice in that (POETIC justice),
2 What those taking flight (plane) inevitably end up doing (LAND) with those finishing with 15 across (finishing ‘cloud cuckoo land’ = LAND),
3 Designed (= anagram indicator) denim cap (denim cap = PANDEMIC) that could be a killer if it goes global (PANDEMIC),
4 Rising (reverse indicator) – not (not = TO-N-) about women (-W-) (TOWN) in urban area (TOWN),
5 Pull a fast one (DELUDE) on Bob getting out of double bed (‘Bob’ getting out of ‘double bed’ = duleed = DELUDE),
6 Swimmer (SALMON-) from the Spanish (‘the’ = -EL-) city in America (Los Angeles = -LA) (SALMONELLA) with stomach-turning bug (SALMONELLA),
7 Leaving (GOING-) one of those in Trinity (one in The Trinity: Father, Son and Holy Spirit = -S ON) (GOINGS-ON) synonymous with dodgy behaviour (GOINGS-ON)
13 Turns up (= reversal indicator), popular (in = -NI-) bird (emu = -UME-) caught (-C-) in Chantilly, for example (Chantilly lace = EC-AL) (ECUMENICAL), is used to promote unity (ECUMENICAL),
14 Makes jokes about (MOCKS) the local trials many with class have to do before leaving (trials/tests ‘locally’ before the Leaving Cert = MOCKS),
16 Jazz (= anagram indicator) ballad (ballad = LA-DABL-) about university (-U-) sweetheart (‘swEet’ heart = -E) (LAUDABLE) is worthy of praise (LAUDABLE)
17 Gets fired (artillery/guns = ORDNANCE) from The Arsenal (arsenal/collection of weapons = ORDNANCE),
19 Key (music key = E-) to sad (= anagram indicator) dirge (dirge = -DGIER) (EDGIER) that’s more provocative (EDGIER),
21 Managed somehow (MADE DO) off one’s head (MAD-) recalling (= reverse indicator) poem (ode = -E DO) (MADE DO),
23 Promise (OATH) of a hot (a hot) dish (= anagram indicator) (a hot = OATH),
24 Worn out (SHOT) by reps from Hot Press (‘reps’ from ‘Hot Press’ = hots = SHOT).