Great singer keen to make comeback (4)
I believe the answer is:
diva
'great singer' is the definition.
(I've seen this before)
'keen to make comeback' is the wordplay.
'keen' becomes 'avid' (I've seen this before).
'to make comeback' says the letters should be written in reverse (I've seen 'making comeback' mean this).
'avid' reversed gives 'DIVA'.
(Other definitions for diva that I've seen before include "For example Sutherland" , "Operatic female singer" , "Distinguished female singer" , "Celebrated female operatic star" , "demanding woman" .)