Solution to 17A 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
8 Essential and wrong! Almost like endless church service at 3 pm! (4,3,3) SINE QUA NON {SIN}{EQUAl}{NONe}
9 Left out flat window glass (4) PANE PANEl (Correction PlANE - See comment)
10 Once more straighten out in opposition to one's character (7,3,5) AGAINST THE GRAIN {AGAIN}{STRAIGHTEN*}
11 Measure of certain lie repeated to an old rock group overshadowed by younger ones! (6) INLIER [T]
14 Heartless brothel keeper gets lady's address (4) MAAM MAdAM
15 Assimilator took nourishment at home, possibly for materialisations (3,2) ATE IN {ATE IN+ASSIMILATOR}*=MATERIALISATIONS [CA]
16 Born dead desire (4) NEED {NEE}{D}
17 Lecherous discreet royal, one coming in for date (8) ?R?R?E?T (Addendum - PRURIENT PRU(-d+r1}RIENT - See comments)
18 Runs ahead for taste! King runs for fun! (6) FROLIC {F(+r)RO(-r)}{LICk}
22 Do rise and vibe excitedly with rich variety of life! (10) BIODIVERSE*
DOWN
1 Receiving a riper kind of flowering ivy (8,7) VIRGINIA CREEPER*
3 Underground bus tips over to ride on sea! Great! (10) SUBSURFACE {BUS<=}{SURF}{ACE}
4 Popular place hosting most honest chaps making piece of orchestral music (15) INSTRUMENTATION {IN}{S{TRUe}{MEN}TATION}
5 Occasionally king eyes a part of leg (4) KNEE {KiNg+EyEs}
7 Destroying Persian militia, saving millions for policy of opposition to dominance over other nations (4-11) ANTI-IMPERIALISM {PERSIAN+MILITIA}* over {M}
Reference List
Left = L, Indian mantra = OM, Born = NEE, Royal = R, Date = D, Dead = D, Runs = R, King = K, Popular = IN, Millions = M, Cocaine = C, Detective = PI(Private Investigator), Book = B

