Treason destroyed politician (7)
I believe the answer is:
senator
'politician' is the definition.
(I've seen this before)
'treason destroyed' is the wordplay.
'destroyed' is an anagram indicator.
'treason' is an anagram of 'SENATOR'.
(Other definitions for senator that I've seen before include "Treason committed by member of Upper House" , "Member of the Upper House of the US Congress" , "US legislator" , "Member of the Second House" , "US/Roman politician" .)