Treason involved politician (7)
I believe the answer is:
senator
'politician' is the definition.
(senator is a kind of politician)
'treason involved' is the wordplay.
'involved' indicates anagramming the letters (involved can mean confusing or complex).
'treason' is an anagram of 'SENATOR'.
(Other definitions for senator that I've seen before include "Upper house US Congressman" , "Roman legislator" , "Member of upper house of legislature" , "Member of the Upper House of the US Congress" , "One from uni's governing body" .)