Girl could be Roman (5)
I believe the answer is:
norma
'girl' is the definition.
'could be roman' is the wordplay.
'could be' is an anagram indicator.
'roman' with letters rearranged gives 'NORMA'.
(Other definitions for norma that I've seen before include "Female" , "Bellini opera - girl's name" , "Manor (anag.)" , "Shearer or Major" , "Roman (anag) - girl's name" .)