Across:
8 Guaranteed Irish (“Guaranteed Irish” = SLOGAN) loans (loans = SLO-AN) arranged around Gulf (-G-) (SLOGAN),
9 Fair amount of (half of) celebrity (star) (half of ‘star’ = AR-) opponents (-RIVALS) (ARRIVALS) providing access to Charles de Gaulle, for one (providing access to Charles de Gaulle, for one airport = ARRIVALS),
10 It’s for fighting (WAR-) dementia initially (‘dementia’ initially = -D) (WARD) in hospital (WARD),
11 Used by 14 across to get rid of intruders (‘gardener’ uses WEED KILLER) with pot (WEED) that could be the death of you (KILLER) (WEED KILLER),
12 Won’t allow a bad word said against anyone on screen (CENSOR) and is bound to clean up (CENSOR),
14 Adam perhaps (GARDENER from Garden of Eden) is in on the plot (GARDENER),
15 It’s permitted (LEGAL) to get a job (PROFESSION) (LEGAL PROFESSION) in the bar (LEGAL PROFESSION),
18 Everyone (all = -LLA-) retiring (= reversal indicator) in Crete (Crete = CE-RET) movement (= anagram indicator) (CELLARET) can hold their drink historically (CELLARET),
20 Don’t bring any attention to (IGNORE) Gore in (Gore in = IGNORE) trouble (= anagram indicator),
22 Scrap (= anagram indicator) value (value = VAU-LE) including 6 down, for example (‘evil person’ = -DEVIL-) (VAUDEVILLE) the old showy type (VAUDEVILLE),
24 Describe a transgression buried in (‘describe a transgression’ buried in = BEAT) Pulse (BEAT),
25 Spokesman (ADVOCATE) for champion (champion/support = ADVOCATE),
26 Cancelled withdrawals by the three banks (‘cancelled withdrawals’ by the three banks = CANALS) for the man-made flowers? (CANALS).
Down:
1 Let out (-LEASE) pressure (P-) first (= position indicator) (PLEASE), if you don’t mind (PLEASE),
2 Part of package deal (part of ‘package deal’ = AGED) for mature wine, perhaps (AGED),
3 Donors (donors = SNO-DRO-) freely (= anagram indicator) welcome work (-W-) at park (-P-) (SNOWDROP) in the spring garden (SNOWDROP),
4 Part of the scuba reconnaissance (part of the “scuba reconnaissance” = BARE) is exposed (BARE),
5 Hasn’t got a penny (BROKE-) from writing (from 3R’s = -R) (BROKER) agent (BROKER),
6 Wild (= anagram indicator) lovers pine (lovers pine = EVIL PERSON) for underworld boss? (EVIL PERSON),
7 Make modifications to (ALTER) direction (direction east = E-) on green light (-GO) (ALTER EGO) for the other half (ALTER EGO),
13 Lad presumably has a job opening it (stable lad has a job opening STABLE DOOR) for firm (STABLE) on the way out (DOOR) (STABLE DOOR),
14 Opens gin (opens ‘gin’ = G-) for party boss (-HOST) (GHOST) – it’s an unbelievable spirit (GHOST),
16 Criminal (= anagram indicator) leaders (leaders = E-ERALDS) seizing one thousand (Roman 1,000 = -M-) (EMERALDS) green gems (EMERALDS),
17 Proof (EVIDENCE) of what 15 across either supports or rebuts (‘legal profession’ either supports or rebuts EVIDENCE),
19 It’s taken from relatives (‘its’ taken from ‘relatives’ = relave = REVEAL) for show (REVEAL),
21 Without a doubt (REALLY), it’s a meeting (R-ALLY) about drugs (ecstasy = -E-) (REALLY),
23 Check out (LEER) Shakespearean character (“Lear” = “LEER”) on the radio (= homophone indicator),
24 Crowd (BAND) responsible for 24 across, for instance (BAND is responsible for ‘beat’).