Clean by scrubbing (5)
I believe the answer is:
scour
'clean by scrubbing' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for scour that I've seen before include "Clean by hard rubbing" , "Hunt through" , "Rub hard or search thoroughly" , "scrub and scrape" , "Comb" .)