US politician’s upsetting treason (7)

I believe the answer is:

senator

'us politician's' is the definition.
(I've seen this before)

'upsetting treason' is the wordplay.
'upsetting' is an anagram indicator.
'treason' is an anagram of 'SENATOR'.

(Other definitions for senator that I've seen before include "Upper house US Congressman" , "Legislative body member" , "One of 100 on Capitol Hill" , "Member of upper US assembly" , "Governor" .)

I've seen this clue in The Times.

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