Cheats, diddles (4)
I believe the answer is:
cons
I believe this clue is a double definition.
'cheats' is the first definition.
(conning is a kind of cheating)
'diddles' is the second definition.
('con' can be a synonym of 'diddle')
(Other definitions for cons that I've seen before include "Arguments against" , "Tricks" , "Swindles" .)