The unclued lights, two of two words and the others as four pairs, are of a kind.

Across

6 Rickety car – one cut off during July (6)

10 House-doctor, game to assist poor maintenance of biological conditions (12)

11 Ten expressions of 14 – just small amounts (5)

14 Appreciation from US actor (6)

17 Drafts of collages (8, hyphened)

21 Did a nose suffer from them? (8)

26 One gets caught in it! (3)

28 Conductors of new trams, that is (7)

35 Department heads of operational research need experience (4)

36 Sombre at first, then dark, then bright (6)

38 Gusher shows how to avoid any friction (7, two...