2647: Pabulum’s last bow

This is Pabulum’s last regular puzzle, though he will continue to appear from time to time. Two pairs of unclued lights give examples of the theme word. Remaining unclued lights each contain a thematic element: a relevant name (6) will appear in the completed grid and must be shaded.

Across

4    Coccid growing short wing (3,6)

10    Bowman supporter backs with a spear I dropped (10)

11    Named Tory youths pelt maniac (6)

14    Scotch swagger (5)

15    Brass pipe they installed (5)

16    A casual drive also cycling allowed (6)

23    Maybe Archie arrests badly hurt Atli’s killer (7)

24    At first lathyrus then tare (4)

25    Chart sailor starts to amend carefully (4)

27    Sober pair of unionists fondly offering lots of milk (7)

29    Much electric potential gave Tom lead in lively plays (8)

32    Flute’s role in truth is bellows-mender (5)

35    Musical pipe senior minister curses (5)

36    Innkeepers line and iron dresses (7)

37    With lost power to breathe I turn blue (6)

38    Ritualistic finance minister one almoner riled (10)

39    Henry’s rude reply to blacken cross-reference (9)

40    Welshman in river terrapin crosses (5)

Down

2    Minister snubbed page (5)

3    Fury over English snowdrift (6)

4    Painter and engineer, each posh (7)

5    Scarily China keeps preparing for war (10)

6    Particular atom exists, too odd to classify briefly (7)

7    Person with base in Asian city (5)

8    Chieftain in chariot cheers up a stunted stubborn type (9)

9    Electronic fan rotating air (4)

13    Dwelling too much in prison (7)

15    Fixer educated in banks (6)

17    Censure American for one surgical task (10)

18    One OTT sim spread type of communist rule (7)

19    Subtle sour lunatic is noisy (10)

20    Empress of India or orange-wife? (5,4)

21    Fashion house takes against...