Style of haircut! (3)
I believe the answer is:
air
'style' is the definition.
(thesaurus)
'of haircut' is the wordplay.
'of' indicates the answer is hidden within the clue.
'AIR' is hidden within 'haircut'.
(Other definitions for air that I've seen before include "Tune - mood - atmosphere" , "Mixture of gases needed for breathing" , "Simple composition" , "Gas mix surrounding the earth" , "It's a mixture mainly of oxygen and nitrogen" .)