Tried in dispute not to cheat (6)
I believe the answer is:
tested
'tried' is the definition.
('tested' can be a synonym of 'tried')
'in dispute not to cheat' is the wordplay.
'in dispute' becomes 'contested' (I've seen this before).
'not' suggests deleting specific letters.
'to cheat' becomes 'con' (con is a kind of cheat).
'contested' with 'con' taken away is 'TESTED'.
(Other definitions for tested that I've seen before include "Subjected to examination or trial" , "Proved" , "Subjected to examination, put through paces" , "Probed or analysed" , "Trialled" .)