Blemish on skin develops, we hear (6)
I believe the answer is:
bruise
'blemish on skin' is the definition.
'develops we hear' is the wordplay.
'develops' becomes 'brews'.
'we hear' shows a homophone (sound like).
'brews' is a homophone of 'BRUISE'.
(Other definitions for bruise that I've seen before include "Discoloured injury" , "Discolouration left by a blow" , "Contusion" , "Sign of injury" , "Superficial injury" .)