Across:
8 Source of wool (ALPACA) in Alabama (AL-), Pennsylvania (-PA-) and California (-CA) (ALPACA),
9 Most of those in 23 down (most of ‘reds’ = RED-) and 24 across (‘wood’ = -WOOD-) on top of Sleeping (top of ‘Sleeping’ = -S) (REDWOODS) Giants native to America (REDWOODS),
10 Leaves home (TREE) and is found in 24 across (TREE is found in ‘wood’),
11 A set of funny pictures in The Paper (COMIC STRIP) for comedienne’s (comic’s = COMIC S-) tour (-TRIP) (COMIC STRIP),
12 Constant (C-) noisy (-LOUD-) calls for the last of (‘callS’ for the last of = -S) (CLOUDS) the sun blocks (CLOUDS),
14 Doctor (doctor/tamper = MESS WITH) produces dog’s dinner (MESS) to humour (WIT-) handler initially (‘Handler’ initially = -H) (MESS WITH),
15 New England state (RHODE ISLAND) opens 22 across (opens ‘red admiral’ = RED-) for endless (end ‘lesS’ = -S) (RHODE ISLAND REDS) chickens (breed of chicken = RHODE ISLAND REDS),
18 Taints (CORRUPTS) at the start of The Captive (at the start of the ‘Captive’ = C-), the ultimate narrator (the ultimate ‘narratoR’ = -R-) in Proust (Proust) novel (= anagram indicator) (Proust = -OR-UPTS) (CORRUPTS),
20 Velázquez’s first (‘Velázquezs’ first = V-) connection to Goya (Goya) travelling (= anagram indicator) (Goya = -OYAG-) to Spain (-E) (VOYAGE) involves a journey overseas (VOYAGE),
22 Flighty type comfortable on two wings (RED ADMIRAL butterfly) playing (= anagram indicator) Real Madrid (Real Madrid = RED ADMIRAL),
24 Deal (deal WOOD) with worthiest of blood banks (‘WOrthiest of bloOD’ banks = WOOD),
25 Father (REVEREND) English (-E-) at the end of summer (at the end of ‘summeR’ = -R-) in Denver (Denver) order (= anagram indicator) (Denver = REV-END) (REVEREND),
26 Security (SAFETY) for head of state (head of ‘State’ = S-) meets armed Head (‘Armed’ head = -A-) Cheese (feta) briefly (a) (‘feta’ without ‘a’ = -FET-) at Yard (-Y) (SAFETY).
Down:
1 Type of arrangement (FLORAL arrangement) all for (all for) mischief (= anagram indicator) (all for = FLORAL),
2 What he is (MALE) to most of those in 14 down (most ‘males’ = MALE),
3 March from the centre (‘mARCh’ from the centre = -ARC-) is (-IS-) heading straight (heading ‘Straight’ = -S-) into Northern Ireland (NI = N-I) (NARCISSI) offering flowers (NARCISSI),
4 Knock back (= reversal indicator) strong liquor (marc = CRAM) in study at the last minute (CRAM),
5 Orders (EDICTS) copies of Proclamation! (EDICTS),
6 Serves up (= reverse indicator) medicinal herb (yarrow) without a (a) (‘yarrow’ without ‘a’ = yrrow = WORRY) natural fibre (cotton)? Without a starter (c) (‘cotton’ without ‘c’ = otton = NOT TO) (NOT TO WORRY) it’ll be fine! (NOT TO WORRY),
7 Conceded (ADMITTED) New (= anagram indicator) Media (Media = ADMI-E-) is about race (-TT- race) to deliver capital (‘Deliver’ capital = -D) (ADMITTED),
13 The type of person with grave responsibilities (UNDERTAKER) you’ll probably have to meet in passing? (UNDERTAKER),
14 Incomplete (p) travel aid (‘map’ without ‘p’ = MA-) for the foreign (‘the’ foreign = -LES) (MALES) drones (= male bees = MALES),
16 Cleaned up (HOOVERED) in flutter (hover = HO-VER-) including tip on outsider (tip on ‘Outsider’ = -O-) from journalist (-ED) (HOOVERED),
17 Rare (NOVEL-) award at university (first = 1st = -IST) (NOVELIST) for Joyce (NOVELIST),
19 Nero’s not included in proper names (‘Neros’ not included in ‘proper names’ = prpeam = PAMPER) for baby? (baby/spoil = PAMPER),
21 Development (GROWTH) of great (G-) argument (-ROW-) with the (the) brief (e) (‘the’ without ‘e’ = -TH) (GROWTH),
23 Shady types (REDS) raised (= reverse indicator) in Palais de Rumine (in ‘palaiS DE Rumine’ = sder = REDS),
24 Partner (WIFE) with swine fever cuts nerves (‘swine fever’ cuts ‘nerves’ = wife = WIFE).