Neglect exploit by detectives (6)
I believe the answer is:
disuse
'neglect' is the definition.
(I've seen this before)
'exploit by detectives' is the wordplay.
'exploit' becomes 'use' (use is a kind of exploit**).
'by' is a charade indicator (letters next to each other).
'detectives' becomes 'dis' (Detective Inspectors, DIs).
'use' put after 'dis' is 'DISUSE'.
(Other definitions for disuse that I've seen before include "Fall into this state to be unemplyed? (6)." , "Issued (anag)" , "State of not being employed" , "Neglect; abandonment" , "Neglect; desuetude" .)