Was chief of detectives: rank? (6)
I believe the answer is:
rancid
'rank?' is the definition.
(thesaurus)
'was chief of detectives' is the wordplay.
I cannot really see how this works, but
'detectives' could be 'cid' and 'cid' is located in the answer.
The remaining letters 'ran' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rancid that I've seen before include "(Of fats) stale" , "Stale, rank" , "Smelly and going bad" , "Sour like stale fat" , "Turned - foul-smelling" .)