Drop brush (5)
I believe the answer is:
scrub
This clue is a double definition.
'drop' is the first definition.
(I've seen this before)
'brush' is the second definition.
(scrub brush is a kind of brush)
(Other definitions for scrub that I've seen before include "Eradicate" , "Clean thoroughly - cancel" , "Abandon" , "Clean - scrap" , "Cleanse" .)