A clear case for the can: crooked and bad (6)
I believe the answer is:
rancid
'bad' is the definition.
(I've seen this before)
'a clear case for the can crooked' is the wordplay.
'a clear' becomes 'rid' (I've seen this before).
'case for' means one lot of letters goes inside another.
'crooked' indicates an anagram.
'can' is an anagram of 'anc'.
'rid' enclosing 'anc' is 'RANCID'.
'and' is the link.
(Other definitions for rancid that I've seen before include "(Of fatty foods) stale" , "Tasting or smelling sour, butter say" , "Stale, rank" , "Fetid" , "(Of butter) stale" .)