Con warder (5)
I believe the answer is:
screw
I believe this clue is a double definition.
'con' is the first definition.
(both can mean to defraud or cheat)
'warder' is the second definition.
(screw can mean a prison warden)
(Other definitions for screw that I've seen before include "Threaded fixer" , "Cheat" , "shot in pool hall" , "Prison officer (sl.)" , "The Turn of the ___ , 1898 Henry James horror story" .)