Mate is bad company (4)
I believe the answer is:
team
'company' is the definition.
(I've seen this before)
'mate is bad' is the wordplay.
'is bad' indicates an anagram (I've seen 'being bad' mean this).
'mate' anagrammed gives 'TEAM'.
(Other definitions for team that I've seen before include "Cooperating group" , "A set of players or workers" , "eleven?" , "Two or more working together" , "Competitive side" .)