Passionate study in art (6)
I believe the answer is:
ardent
'passionate' is the definition.
('ardent' can be similar in meaning to 'passionate')
'study in art' is the wordplay.
'study' becomes 'den' (I've seen this before).
'in' means one lot of letters goes inside another.
'den' inserted into 'art' is 'ARDENT'.
(Other definitions for ardent that I've seen before include "Intensely enthusiastic" , "very interested" , "Passionate and glowing" , "Loving and fiery" , "Passionate, fervent" .)