Green’s Dictionary of Slang

a sorting-out.

1940		‘Operator 1384’ McCann the Spy 263: McCann and I took ten men each and made a systematic comb-out of the Gardens. Every sniper we found we shot out of hand .
1943		in T. Harrisson Mass-Observation War Factory: Report 1: I’d like to see a good comb-out up there, to catch out these sort of people.
1969		(con. WW1) A.R. Cooper Born to Fight 224: [W]e were stopped by ten police mobile [...] this was one of the periodic comb-outs of streets in which the police hoped to catch criminals unawares .