Cheating ruled out as dodgy (10)
I believe the answer is:
adulterous
'cheating' is the definition.
('adulterous' can be a synonym of 'cheating')
'ruled out as dodgy' is the wordplay.
'dodgy' indicates an anagram.
'ruled'+'out'+'as'='ruledoutas'
'ruledoutas' with letters rearranged gives 'ADULTEROUS'.
(Other definitions for adulterous that I've seen before include "Betraying a legal partner" , "untrue" .)