Fiery study in art (6)
I believe the answer is:
ardent
'fiery' is the definition.
('ardent' can be a synonym of 'fiery')
'study in art' is the wordplay.
'study' becomes 'den' (I've seen this before).
'in' means one lot of letters goes inside another.
'den' put within 'art' is 'ARDENT'.
(Other definitions for ardent that I've seen before include "Passionate and glowing" , "Enthusiastic or passionate" , "Fiery and passionate" , "Passionate, full of feeling" , "Zealous - ranted (anag)" .)