Engrossed artist emptied paint (4)
I believe the answer is:
rapt
'engrossed' is the definition.
('rapt' can be a synonym of 'engrossed')
'artist emptied paint' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'emptied' means to remove the middle letters.
'paint' with its middle removed is 'pt'.
'ra'+'pt'='RAPT'
(Other definitions for rapt that I've seen before include "Completely absorbed" , "Engrossed, spellbound" , "'Transported, entranced (4)'" , "Part being transported" , "Spellbound in part" .)