Treason would ruin this politician (7)

I believe the answer is:

senator

I'm a little stuck... Click here to teach me more about this clue!

'politician' is the definition.
(senator is a kind of politician)

'treason would ruin' is the wordplay.
'treason' anagrams to 'SENATOR'.
Though, I am not clear how this is indicated.

'this' acts as a link.

Can you help me to learn more?

(Other definitions for senator that I've seen before include "Member of Upper House engaged in treason" , "US/Roman politician" , "Roman politician" , "Politician involved in treason" , "Member of the Second House" .)

I've seen this clue in the Evening Standard.

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