Look bad-tempered, it's said (4)
I believe the answer is:
mien
'look' is the definition.
(mien means a look or impression)
'bad-tempered it's said' is the wordplay.
'bad-tempered' becomes 'mean' (I've seen this before).
'it's said' shows a homophone (sound like).
'mean' is a homophone of 'MIEN'.
(Other definitions for mien that I've seen before include "A face like mine" , "The carriage" , "A face - maybe mine" , "Person's bearing" , "Personal bearing" .)