Brush hard to clean (5)
I believe the answer is:
scrub
'brush hard to clean' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for scrub that I've seen before include "Scour - stunted trees" , "Cleanse" , "Clean with hard brush and soapy water" , "Rough country area" , "Rub hard to clean" .)