Lacking refinement, energy - in finish lost (9)
I believe the answer is:
engrossed
'lost' is the definition.
(thesaurus)
'lacking refinement energy in finish' is the wordplay.
'lacking refinement' becomes 'gross'.
'energy' becomes 'e' (physics symbol as in E=mcn).
'in' is an insertion indicator.
'finish' becomes 'end' (synonyms).
'gross'+'e'='grosse'
'grosse' going within 'end' is 'ENGROSSED'.
(Other definitions for engrossed that I've seen before include "Deeply engaged" , "Complete absorbed, rapt" , "'Rapt, immersed (9)'" , "occupied" , "Consumed" .)