Expert's finished (12)
I believe the answer is:
accomplished
This clue is a double definition.
'expert's' is the first definition.
('accomplished' can be a synonym of 'expert')
'finished' is the second definition.
(thesaurus)
(Other definitions for accomplished that I've seen before include "Skilled; done" , "Done - with a high degree of skill" , "Having particular skills" , "Expert - done" , "executed" .)