Treat is arranged for entertainer (7)
I believe the answer is:
artiste
'for entertainer' is the definition.
(artiste is a kind of entertainer)
'treat is arranged' is the wordplay.
'arranged' indicates an anagram.
'treat'+'is'='treatis'
'treatis' is an anagram of 'ARTISTE'.
(Other definitions for artiste that I've seen before include "Tears it (anag.)" , "Theatre performer" , "One entertaining" , "'Public performer, dancer or singer (7)'" , "A sitter for a performer" .)