US politician upsetting one star (7)
I believe the answer is:
senator
'us politician' is the definition.
(the US has a senate)
'upsetting one star' is the wordplay.
'upsetting' is an anagram indicator.
'one'+'star'='onestar'
'onestar' anagrammed gives 'SENATOR'.
(Other definitions for senator that I've seen before include "Roman legislator" , "Member of the Upper House of the US Congress" , "Statesman -- treason (anag)" , "Clinton, perhaps" , "Member of Upper House engaged in treason" .)