Professional performer: I start dancing, beginning to entertain (7)
I believe the answer is:
artiste
'professional performer' is the definition.
(I've seen this before)
'i start dancing beginning to entertain' is the wordplay.
'dancing' is an anagram indicator.
'beginning to' indicates taking the first letters.
The initial letter of 'entertain' is 'e'.
'i'+'start'='istart'
'istart' is an anagram of 'artist'.
'artist'+'e'='ARTISTE'
(Other definitions for artiste that I've seen before include "professional dancer?" , "Entertainer, singer or dancer" , "A sitter for a performer" , "'Public performer, dancer or singer (7)'" , "nightclub entertainer?" .)