Look nasty, we hear (4)
I believe the answer is:
mien
'look' is the definition.
(thesaurus)
'nasty we hear' is the wordplay.
'nasty' becomes 'mean' ('mean' can be similar in meaning to 'nasty').
'we hear' indicates a 'sounds like' (homophone) clue.
'mean' is a homophone of 'MIEN'.
(Other definitions for mien that I've seen before include "Dignified manner" , "Personal bearing" , "Person's bearing" , "Facial expression sounds miserly" , "(One's) manner, bearing" .)