Con fixer (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)
'fixer' is the second definition.
(I have seen 'Threaded fixer ' mean 'screw' so perhaps 'fixer' could also mean 'screw')
(Other definitions for screw that I've seen before include "Take advantage of" , "Fastener with a tapered threaded shank" , "Archimedes' invention" , "little twister!" , "Metal fastener" .)