Caught working fiddle (3)
I believe the answer is:
con
'fiddle' is the definition.
'caught working' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'working' becomes 'on'.
'c'+'on'='CON'
(Other definitions for con that I've seen before include "Swindle after winning trust" , "Tory" , "Dupe" , "Deceive (someone)" , "Defraud" .)