Thick head of hair (3)
I believe the answer is:
mop
'thick head of hair' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mop that I've seen before include "Clean; mass of hair" , "Floor wiper" , "Floor cleaner" , "Polish" , "Finish off a task - . . . up" .)