This sharpens good skin's colour (10)
I believe the answer is:
grindstone
'this sharpens' is the definition.
The definition suggests a singular noun which matches the answer.
'good skin's colour' is the wordplay.
'good' becomes 'g' (abbreviation).
'skin's' becomes 'rinds' ('rind' can be a synonym of 'skin').
'colour' becomes 'tone' (tone can mean a colour or shade).
'g'+'rinds'+'tone'='GRINDSTONE'
Can you help me to learn more?
(Other definitions for grindstone that I've seen before include "nosing here?" , "Tool sharpener" , "This hones blade" , "Disc for sharpening knives" , "Blade sharpener" .)