Cowl (4)
I believe the answer is:
hood
'cowl' is the definition.
(I know that cowl can be written as hood)
This is all the clue.
(Other definitions for hood that I've seen before include "Bonnet (US) - gangster (US)" , "Capital cover" , "See 8" , "Protective cover - violent criminal (slang)" , "Head covering or American car bonnet" .)