Messy hairdo (3)
I believe the answer is:
mop
'messy hairdo' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mop that I've seen before include "Finish off a task - . . . up" , "Polish" , "Floor cleaner" , "Tangle of hair" , "Shock of hair; soak (up)" .)