Scrubs hard (6)
I believe the answer is:
scours
'scrubs hard' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for scours that I've seen before include "runs for cattle" , "Cleans by hard rubbing." , "Cleans by rubbing with rough material" , "Searches thoroughly or cleans abrasively" , "Rushes along" .)