Managed detectives, but became sour (6)
I believe the answer is:
rancid
'sour' is the definition.
(I know that sour can be written as rancid)
'managed detectives' is the wordplay.
'managed' becomes 'ran' (both can mean organised or was in charge of).
'detectives' becomes 'CID' (abbreviation for Criminal Investigation Department).
'ran'+'cid'='RANCID'
'but became' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for rancid that I've seen before include "Fragmented bricks etc." , "Sour like stale fat" , "Turned - foul-smelling" , "Like fat that's gone off" , "Putrid" .)