Hard work, scrubbing good skin (4)
I believe the answer is:
rind
'skin' is the definition.
(synonyms)
'hard work scrubbing good' is the wordplay.
'hard work' becomes 'grind' (I've seen this before).
'scrubbing' is a deletion indicator.
'good' becomes 'g' (abbreviation).
'grind' with 'g' taken away is 'RIND'.
(Other definitions for rind that I've seen before include "'Peel, bark (4)'" , "tough skin" , "Outer edge of a bacon rasher" , "Zest" , "Skin of bacon" .)