Cut crest on trim scrub (5)
I believe the answer is:
clean
'scrub' is the definition.
(I know that scrub is a more specific form of lave)
'cut crest on trim' is the wordplay.
'cut crest on' becomes 'c' (I can't explain this - if you can you should give a lot more credence to this answer).
'trim' becomes 'lean' (similar in meaning).
'c'+'lean'='CLEAN'
Can you help me to learn more?
(Other definitions for clean that I've seen before include "not spotted" , "How confessor comes" , "far from blue" , "remove filth" , "Free from contamination - entirely" .)