Replacement definitions (26 words in total, either singly or consecutively in the same clue) must be removed from 19 clues before solving.
What's left is to be treated thematically in order to resolve all clashes and successfully complete the grid.
The theme title should be written beneath the grid. (3,5,3)
Chambers Dictionary is the primary reference. Two answers are found in OED. Two answers are abbreviations. One answer is in Collins.

Across 1.Secure and elegant gilded case (6) 4.Whipped boy takes female captive (6) 10.Blackmail soldiers into reformation.(8) 12.Seldom arranged measures without small payment (4) 13.Stubborn Native American chicken moving about to end. (5) 15.'No go' region wear a mask.(10) 16.It's rough being dragged back in Italy, remember.(5) 17.Campbells,perhaps, left space in tins.(5) 18.Arrest IOC representation for civil unrest.(2 words) 21.Mission: Return those not coming back from the war.(3) 23.Take heart from opposition's broadcast (3) 24.Busy carpet lifts the art of building (9) 25.Bills reduce mileage time (5) 28.Finishes Charlie off and drops Mark (5) 30.Listened to track on the Heaviside Layer perhaps.(2 words) 32.Find a change to last forever (2 words) 33.Takes edges off dark coloured bloomers. (4) 34.Most got their words muddled,Randy lets suit out.(8) 35.Poet's from Siberia and does AM shift.(6) 36.Has former prostitutes taking lethal dose.(6)

Down 1.Those who stake claim to decrepit beavers perhaps. (7) 2.Gather together least practised and pay for call at the other end in Chicago. (7) 3.Return to East Caribbean house gatherings (4) 4.They don't give you much time to settle a coin toss (11 two words) 5.It may be passed for a seat? (5) 6.Ethan naughtily embraces Barbera's partner (5) 7.Trades one in, wheelless conveyance, send it back (5) 8.Look over second tower (4) 9.Pin decoration on permit (6) 11.Chinese took a chance to include brief program and put on weight (11) 14.Be sorry for long lasting hour out of shape (5) 19.Delia's cooking was unhealthy (5) 20.Muzzles for Aberdeen Angus,possibly kept on board(6) 21.First man then ladies troubled to take eye-drop in the wrong direction (7) 22.Insists upon a back strain (7) 25.Originally canine pets had always liked sensitive Romany people (5) 26.Belief in arbitrary force of God is misplaced (5) 27.Theme singer is unable to love piece of music (5) 29.'Hairy' chap, Cockney, was witness to hearing.(4) 31.German odd-jobs man races in spectacles (4)

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