Across:
8 Knockout (knockout = KO-) endless (end ‘lesS’ = -S-) leaders of volatile organisation (leaders ‘Of Volatile Organisation’ = -OVO) (KOSOVO) in a state (KOSOVO),
9 Able (TALENTED) to drink (-ALE-) tea (T-) opening (= position indicator) good books (New Testament = -NT-) by writer (-ED) (TALENTED),
10 Sign (OMEN) for dahl from homeland (‘dahl’ from ‘homeland’ = omen = OMEN),
11 The Rose of Tralee (The Rose of Tralee = FOLK BALLAD) from 24 across (‘folk’ = FOLK) and 26 across (‘ballad’ = BALLAD) (FOLK BALLAD),
12 Investigates (PROBES) The Last Word (postscript = P-S) over cover-up (-ROBE-) (PROBES),
14 Crazy (= anagram indicator) mystics (mystics = SYST-MIC) holding key (music key -E-) (SYSTEMIC) that affects the whole network (SYSTEMIC),
15 Placed on a roster (LISTED) by 25 across (‘building’ = BUILDING-) for school (-S) (LISTED BUILDINGS) with protected structures – technically, we don’t have them here (LISTED BUILDINGS),
18 Some sandy summits (‘Some Sandy’ summits = -SS-) around meandering (= anagram indicator) desert (desert = STRE-ED) (STRESSED) under pressure (STRESSED),
20 Criminal (= anagram indicator) bosses (bosses = OBSESS) think it through relentlessly (OBSESS),
22 If this is not demanding (simple) for the most part (e) (simple’ without ‘e’ = SIMPL-) at first (1st = -IST-), one (-I-) could start (‘Could’ start = -C) (SIMPLISTIC) ignoring real complexity (SIMPLISTIC),
24 People (FOLK) from community (fold) mostly (d) (‘fold’ without ‘d’ = (FOL -) on Cork border (‘corK’ border = -K) (FOLK),
25 What the Masons made (BUILDING) of the Italian (‘the’ Italian = il = -IL-) racket (din = -DIN-) captured by wiretap (bug = BU-G) (BUILDING),
26 A place for scientists (lab) set up (= reverse indicator) (lab = BAL-) by the foreign (‘the’ French = la = -LA-) director (-D) (BALLAD) in the fields of Athenry (Pete St. John’s The Fields of Athenry = BALLAD).
Down:
1 Rome (Rome = -ORME-) butcher (anagram indicator) taken in by father (Fr = F-R) (FORMER) of late (FORMER),
2 It might generate some interest (LOAN generates bank interest) for longshoreman on the banks (for ‘LOngshoremAN’ on the banks = LOAN),
3 Clueless (CONFUSED) as officer (Commanding Officer = CO-) joined up (fused = -FUSED) after (= position indicator) finishing with woman (finishing with ‘womaN’ = -N) (CONFUSED),
4 Late (late) retrospective (= reverse indicator) (late = ET AL) by the others in old Rome (ET AL),
5 Collected (= anagram indicator) basil (basil = ALIB-S) around island (-I-) (ALIBIS) produced by those who may be suspect (ALIBIS),
6 Sing Alsace (sing Alsace) medley (= anagram indicator) (sing Alsace = ANALGESICS) for those in pain (ANALGESICS),
7 Acting in a way (BEHAVING) is doing what you’re told (BEHAVING),
13 Drink (BITTER) to go with port (P-) is not the best (ill = -ILL) (BITTER PILL) and is hard to take? (BITTER PILL is hard to take),
14 Dangerous removing gear (‘dangerous’ removing ‘gear’ = dnous = SOUND) in stretch of water (inlet = SOUND),
16 Popular (IN-) soldier (GI) set up (= reverse indicator) (GI = -IG-) in bona fide (true = -TR-UE) (INTRIGUE) conspiracy (INTRIGUE),
17 Sounds like (= homophone indicator) family (‘line’ = ‘LION) taking empty (r) parking places (curbs) (‘curbs’ without ‘r’ = CUBS) (LION CUBS) for those younger members of Pride (LION CUBS),
19 Staggers (trips) back (= reversal indicator) (trips = SPIR-T) around island (-I-) (SPIRIT) from the bar (SPIRIT),
21 In no time leaves sensationalism (‘in no time’ leaves ‘sensationalism’ = ssaals = SALSAS) to those getting served in Mexican restaurant (SALSAS),
23 Yanks (yanks/pulls = TUGS) and Portuguese dismissing Europe (‘Portuguese’ dismissing ‘Europe’ = tugs = TUGS),
24 Drop (FALL) part of the Oath of Allegiance (part of the ‘oath oF ALLegiance’ = FALL).