Detective's oversight leads to release (7)
I believe the answer is:
dismiss
'release' is the definition.
(thesaurus)
'detective's oversight' is the wordplay.
'detective's' becomes 'dis' (Detective Inspector).
'oversight' becomes 'miss'.
'dis'+'miss'='DISMISS'
'leads to' is the link.
(Other definitions for dismiss that I've seen before include "Throw out" , "Drop" , "P45" , "Sack - cashier" , "Sack - send away" .)