Viscount's superior (4)
I believe the answer is:
earl
'viscount's superior' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for earl that I've seen before include "A real sort of lord" , "-- Grey, PM 1830-34" , "UK nobleman ranking between marquess and viscount" , "Real kind of English lord" , "Count" .)