Fairy’s tune (3)
I believe the answer is:
air
I believe this is a double definition.
'fairy's' is the first definition.
(thesaurus)
'tune' is the second definition.
(air can mean a piece of music)
(Other definitions for air that I've seen before include "Bearing, manner" , "Feel" , "Short song" , "Ventilate with breathing gas" , "Tune or aura" .)