Solution to 12A has been deliberately left unsolved and is to be answered only by a non-regular / novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.
Someone to identify the theme and the theme words.
ACROSS
1 "Fabric is certainly from Germany" — king, maybe while clothing queen (8) JACQUARD {JA}{C{QU}ARD}
6 After backing explosive claims, Gujarat's leader has a problem (6) ENIGMA {M{Gu...t}INE<=}{A}
9 Recess on the counter in office space (4) APSE [T<=]
10 Article with murky origins leads to speculation (10) THEORISING {THE}{ORIGINS*}
11 Desperately tries to chase married man (6) MISTER {TRIES}*<=>{M}
12 Garbage recycled, say, after moving to small waste bins (8) A?H?R?Y? (Addendum - ASHTRAYS {(-tr)ASH(+tr)TR}{SAY*} - See comments)
13 Dr. X's Y? That's it! (3,2,5) END OF STORY {Y is end of story)
15 Hollow, easily forgotten past promise (4) BOND BONeD (Addendum - BeyOND - See comments)
17 Labour blocks its second candidate's aspiration (4) SEAT SwEAT
18 Get rid of water, honey, urn, myrrh (items devotees originally used during worship) (10) DEHUMIDIFY {Ho..y}{Urn}{My..h}{It..s}{De...s} in {DEIFY}
20 Korean vote surprisingly expresses no new change in leadership (8) TAKEOVER {KOREAn+VoTE}*
22 Warden and Woburn, for example, getting bowled for fifty twice in back streets (6) ABBEYS A(-ll+bb)BBEYS
24 Engineer random changes in parent note (10) MEMORANDUM {E}{RANDOM*} in {MUM}
27 Go through dessert, skipping one staple food item (6) PIERCE {PIE}{RiCE}
28 Screamed after suppressing a cry of anguish and turned pale (8) YELLOWED {YELL{OW}ED}
DOWN
2 Can I mash in fruit blender? (9) APPLIANCE {CAN+I}* in {APPLE}
3 Seeking technique studied secretly (5) QUEST [T]
4 Habits of extremely affluent bores (7) ATTIRES {Af...nT}{TIRES}
5 Prescribed food, not timepass! (3) DIE DIEt
6 Sensual and without reservations when out of India, husband moves lower (7) EARTHLY (-h)EART(+h)HiLY
7 "Angry Birds" — nice, impressively written (9) INSCRIBED*
8 Penny perhaps king's taken from fool (5) MONEY MONkEY
12 A different one, found in America, not here (7) ANOTHER [T]
14 Regularly worn hot Nehru cap of officials (2,3,4) ON THE HOUR {HOT+NEHRU+Of...s}*
16 New gas masks gain approval for military manoeuvre (2-3,4) NO FLY ZONE {N}{O{FLY}ZONE}
18 Married woman had to stray (7) DEVIATE {DEVI}{ATE}
21 Asian jazz genre — it's covered frequently (5) AZERI {jAzZ+gEnRe+It}
23 A couple of slices of bread, and eggs over well done (5) BRAVO {BRead}{OVA<=}
25 Period and comma, say, basically? (3) DAY Tail acrostic
Reference List
Certainly in German = JA, Queen = QU, Married = M, Easily = E, Bowled = B, Fifty = L, Engineer = E, India = I, Husband = H, King = K, New = N, Month = M