One who plays a noted part in the theatre (5,6)
I believe the answer is:
opera singer
'one who plays a noted part in the theatre' is the definition.
(person who sings musical notes in a theatre)
This is the entire clue.
(Other definitions for opera singer that I've seen before include "Stage performer" , "Butt perhaps" , "Prima donna" , "La Scala artiste" , "diva" .)