Prima donna keen to make comeback (4)
I believe the answer is:
diva
'prima donna' is the definition.
(I know that prima donna can be written as diva)
'keen to make comeback' is the wordplay.
'keen' becomes 'avid' (both can mean enthusiastic).
'to make comeback' is a reversal indicator (I've seen 'making comeback' mean this).
'avid' in reverse letter order is 'DIVA'.
(Other definitions for diva that I've seen before include "Callas, say" , "Operatic female singer" , "A female opera singer" , "Famous female singer" , "Operatic soprano" .)