Loose way of working police officer rejects (5)
I believe the answer is:
untie
'loose' is the definition.
(loose can mean to untie or unleash)
'way of working police officer rejects' is the wordplay.
'way of working' becomes 'mo' (abbreviation for modus operandi).
'police officer' becomes 'Mountie' (member of the Royal Canadian Mounted Police).
'rejects' is a deletion indicator.
'mountie' with 'mo' taken out is 'UNTIE'.
(Other definitions for untie that I've seen before include "resolve" , "Release from bonds or open shoelace" , "Unite (anag)" , "get rid of bonds" , "Detach" .)