Marilyn Monroe's birth name (5)
I believe the answer is:
norma
'marilyn monroe's birth name' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for norma that I've seen before include "Marilyn was properly one" , "Roman (anag) -- opera" , "Female" , "Roman (anag) - girl's name" , "She incited Gauls v. Romans (Bellini)" .)