Prima donna eager to make a comeback (4)
I believe the answer is:
diva
'prima donna' is the definition.
(I know that prima donna can be written as diva)
'eager to make a comeback' is the wordplay.
'eager' becomes 'avid' (synonyms).
'to make a comeback' says the letters should be written in reverse (I've seen 'making a comeback' mean this).
'avid' back-to-front is 'DIVA'.
(Other definitions for diva that I've seen before include "Operatic ego" , "Prima dona" , "Distinguished female singer" , "Top opera singer" , "Great performer" .)