What chief detective did is bad (6)
I believe the answer is:
rancid
'is bad' is the definition.
(I've seen this in another clue)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rancid that I've seen before include "Rank-smelling." , "Smelling or tasting of stale fat" , "Rotten; high" , "Stale, with an offensive smell" , "(Of fatty foods) stale" .)