Use elbow grease on (5)
I believe the answer is:
scour
'use elbow grease on' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for scour that I've seen before include "Look high and low" , "Clean by scrubbing" , "purge" , "Rub with a gritty substance" , "Clean - scout" .)