Across:
8 Flipping (= reverse indicator) politician (Member of the Legislative Assembly = MLA = ALM-) in charge of the party (host) loses the head (h) ('host' without 'h' = -OST) (ALMOST), more or less (ALMOST),
9 Celebrity (name) is upset (= reverse indicator) (name = EM-AN) over funeral pile (-PYRE-) (EMPYREAN) in heavenly place, poetically speaking (EMPYREAN),
10 Shot (SNAP) of crack (SNAP),
11 Presumably you could buy this from 20 across (gasman) (OXYGEN) and from relative (MA-) from Saskatchewan (-SK) (OXYGEN MASK), for one taking a breather (OXYGEN MASK),
12 Month (OCT-) before (= positional indicator) Ireland (Republic of Ireland = -ROI) (OCTROI) could use this to raise old tax (OCTROI),
14 A (A-) boxer (pet dog = -PET-) getting it (-IT-) in gym (PE = -P-E) (APPETITE) needs to be satisfied, of course (APPETITE satisfied with course/food),
15 One of those giving private tuition (army / DRILL INSTRUCTOR) in showing someone how to work on an oil rig (DRILL INSTRUCTOR),
18 Is accommodating (FLEXIBLE) around fanatical (around ‘FanaticaL’ = FL-) bachelor (-B-) in bar outside the country (exile = -EXI-LE)! (FLEXIBLE),
20 Comedian (GAS MAN) has a job reading things in other people’s homes (GAS MAN),
22 Guide (INSTRUCTOR) for those characters ultimately in 15 across (ultimately in ‘drill instructor’ = INSTRUCTOR),
24 The limits to putting up (= reverse indicator) egomaniac (the limits to raising ‘EGomaniAC’ = egac = CAGE) in place of confinement (CAGE)
25 Swam away from Western Samoa (‘swam’ away from ‘Western Samoa’ = esternoa = RESONATE) – echo that! (RESONATE),
26 Rows with Spud’s (rows with spuds = DRILLS) buddies at the end (‘buddieS’ at the end = -S) after (= position indicator) starting on 15 across (starting on ‘drill instructor’ = DRILL-) (DRILLS).
Down:
1 Teaser from electricians ('teaser' from 'electricians' = lcicin = CLINIC) providing remedies (CLINIC),
2 What you could make with the bones of 6 down (make SOUP with the bones of ‘drumsticks’) as a stock offering? (SOUP),
3 In retrospect (= reverse indicator), it’s (its = ST-I) about rip off (-ROB-) on the Italian (‘the’ Italian = -IL-) (STROBILI) cones (pine/fir tree cones = STROBILI),
4 Refuse to admit (DENY) what’s concealed by the downtrodden youths (what’s concealed by the ‘downtrodDEN Youths’ = DENY),
5 Maintenance (UPKEEP) of university (U-) creates pressure (-P-) on store (store/save = -KEEP) (UPKEEP),
6 Plays in a band (drums = DRUM-S) covering Rod (-STICK-) (DRUMSTICKS) and alternatives to Wings (alternatives to chicken wings = DRUMSTICKS),
7 Fellow (F-), in addition (also = ALS-O) takes in first endurance (first ‘Endurance’ = -E-) race (Tourist Trophy race = -TT-) (FALSETTO) and is vocal we hear (FALSETTO),
13 Mental repose (RELAXATION) of a (-A-) mystery man (-X-) in Oriental (Oriental) novel (= anagram indicator) (Oriental = REL-ATION) (RELAXATION),
14 Seating option (AISLE seat) in a (A-) Capri (-ISLE of Capri) (AISLE),
16 Came around (RELENTED) in a fast time (a fast time = -LENT-) consumed by grass (reed = RE-ED) (RELENTED),
17 Artist (RA-) group – the first (‘Group’ the first = G) to buy and sell (TRADE) (RAG TRADE) clothing business (RAG TRADE),
19 Let in/off bullet train (‘let in’ off ‘bullet train’ = bultra = BRUTAL) by Savage, in manner of speaking? (BRUTAL),
21 Old bank (Anglo) corrupted (= anagram indicator) (Anglo = ANGOL-) a (-A) (ANGOLA) country in west Africa (ANGOLA),
23 Secures (TIES) building (= anagram indicator) site (site = TIES),
24 Two sides in Championship (two sides in ‘CHampionshIP’ = CHIP) you really don’t want to see in China (don’t want to see chip in china plate = CHIP).