A performer in taking part is terrible (7)
I believe the answer is:
Here is my best explanation:
'a performer' is the definition.
(artiste is a kind of performer)
'in taking part is terrible' is the wordplay.
'in' indicates a hidden word.
'ARTISTE' is hidden within 'taking part is terrible'.
(Other definitions for artiste that I've seen before include "Performers", "Theatre performer", "Tears it (anag.)", "Dancer", "professional dancer?", "Entertainer, singer or dancer", "A professional entertainer", "A sitter for creative person", "A public performer" and "Professional performer".)