Fraud could mean case is not even over (4)
I believe the answer is:
scam
'fraud' is the definition.
(scam is a kind of fraud)
'mean case is not even over' is the wordplay.
'is not even' means one should take alternating letters (remove even-numbered letters).
'over' is a reversal indicator.
'mean'+'case'='meancase'
The alternating letters of 'meancase' are 'macs'.
'macs' reversed gives 'SCAM'.
'could' acts as a link.
(Other definitions for scam that I've seen before include "Racket" , "Hoax" , "Swindle (sl.)" , "rook" , "Dodgy business" .)