Twit's betrayal (7)
I believe the answer is:
treason
This could be a double definition.
'twit's' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'betrayal' is the second definition.
(I know that betrayal can be written as treason)
(Other definitions for treason that I've seen before include "Crime of treachery against the state" , "Disloyalty (to one's country)" , "LEse-majestE" , "Stare on (anag.)" , "Mutiny" .)