Fairy of superiority (4)
I believe the answer is:
peri
'fairy' is the definition.
(Persian mythological being)
'of superiority' is the wordplay.
'of' indicates the answer is hidden within the clue.
'PERI' is hidden within 'superiority'.
(Other definitions for peri that I've seen before include "Fairy of Persian folklore" , "Malevolent Persian spirit" , "Old Persian fairy" , "Prefix denoting 'around'" , "Mythical being" .)