A number from Marianne (4)
I believe the answer is:
aria
'a number' is the definition.
(I have seen 'Operatic number ' mean 'aria' so perhaps 'number' could also mean 'aria')
'from marianne' is the wordplay.
'from' indicates a hidden word.
'ARIA' can be found hidden inside 'marianne'.
(Other definitions for aria that I've seen before include "Operatic solo performance" , "Repeated strain" , "Air in an opera" , "Song, one from 'West Side Story' needing no introduction" , "Operatic part" .)