Solution to 8A has been deliberately left unsolved and is to be answered by a non-regular/novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.
Open for anyone to answer, if not solved by 1 PM.
ACROSS
1 Bans pesticide, nasty stuff (4,3,6) BITS AND PIECES*
8 Dim lights entirely at first in pub (5) B?E?R (Addendum - BLEAR {B{Li...s}{En...y}AR} - See comments)
9 Dribbling with energy in east European arena (9) SLAVERING {E} in {SLAV}{RING}
11 Be very surprised by awful heat on set around afternoon (3,4,3) EAT ONES HAT {HEAT+ON+SET}* over {A}
12 Beat culprit stealing bags in retreat (4) STIR [T<=]
16 Kitchen item with good sieve (7) GRIDDLE {G}{RIDDLE}
19 Overwhelmed by drink, member has terribly serious accident (5-2) SMASH-UP {S{M}{HAS*}UP}
21 Trouble after king's murder (4) KILL {ILL}<=>{K}
22 Hero in rave turned intoxicated (10) ADVENTURER*
25 Repaired terminal's railway tracks (9) TRAMLINES*
26 Extremely unruly fool interrupting concert (5) UNITY {Unr{NIT}ulY}
27 Clear-cut kind of film (5-3-5) BLACK-AND-WHITE [DD]
DOWN
2 Thought creatively and edited a novel (7) IDEATED*
3 Most resilient secret agents collaring gang leader in tunnel (10) SPRINGIEST {SP{RING}IES}{Tu...l}
4 Bags filled with special egg holders (5) NESTS {NE{S}TS}
5 Girl transported by plane has broken bones (9) PHALANGES {G} in {PLANE+HAS}*
6 Wife entertained by show about sheep (4) EWES {SE{W}E<=}
7 Victory secured by deceit, rogue's expelled (7) EVICTED {E{V}ICTED*}
10 Start to roll joint with member in merry social event held on lawn (6,5) GARDEN PARTY {Roll}{DEN}{PART} in {GAY}
13 One inspired by macho stud's unusual knack of making money (5,5) MIDAS TOUCH {1} in {MACHO+STUD}*
15 Revolutionary plan to catch brilliant Mafia boss in European region (9) MACEDONIA {AIM<=} over {ACE}{DON}
18 Ancient chamber containing large bag (7) HOLDALL {H{OLD}ALL}
20 Musician in Paris, playing in hotel bar (7) HARPIST {H}{PARIS*}{T}
23 Take a sedative to stay relaxed (5) EASED [T]
24 Starts to beat leader of cocaine cartel (4) BLOC Acrostic
Reference List
Energy = E, Afternoon = A, Master = M, Good = G, Member = M, King = K, Special = S, Girl = G, Wife = W, Victory = V, Hotel = H, Bar = T