Paint messily (4)
I believe the answer is:
daub
'paint messily' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for daub that I've seen before include "Coat with plaster" , "Smear roughly or paint clumsily" , "coat casually" , "Smear; bad painting" , "Amateurish painting" .)