Swindle, con (4)
I believe the answer is:
scam
I believe this clue is a double definition.
'swindle' is the first definition.
(I know that scam is a type of swindle)
'con' is the second definition.
(both can mean a fraudulent scheme)
(Other definitions for scam that I've seen before include "Fraudulent scheme, swindle" , "Fraudulent trick or swindle" , "Fraud, trick (slang)" , "Swindle, fraud (colloq.)" , "Swindle (Slang)" .)