Queen one earl upset (7)
I believe the answer is:
eleanor
'queen' is the definition.
(I've seen this before)
'one earl upset' is the wordplay.
'upset' indicates an anagram.
'one'+'earl'='oneearl'
'oneearl' anagrammed gives 'ELEANOR'.
(Other definitions for eleanor that I've seen before include "Female" , "woman" , "Franklin D. Roosevelt's wife" , "Near Leo (anag) - girl's name" , "Consort of Henry II" .)