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' is an insertion indicator.
'crooked' indicates an anagram (a crooked or disrupted version of the letters).
'can' with letters rearranged gives 'anc'.
'rid' placed around 'anc' is 'RANCID'.
'and' acts as a 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" .)