Tortured senator for disloyalty (7)
I believe the answer is:
treason
'disloyalty' is the definition.
(treason is a kind of disloyalty)
'tortured senator' is the wordplay.
'tortured' indicates anagramming the letters (I've seen this in other clues).
'senator' is an anagram of 'TREASON'.
'for' is the link.
(Other definitions for treason that I've seen before include "Betrayal (of one's country)" , "Crime of national betrayal" , "Deliberate act of betrayal" , "One rats (anag)" , "Crime of disloyalty" .)