Return of opera-singer making you keen (4)
I believe the answer is:
avid
'keen' is the definition.
(both can mean enthusiastic)
'return of opera-singer' is the wordplay.
'return of' is a reversal indicator.
'opera singer' becomes 'diva' (I've seen this in another clue).
'diva' reversed gives 'AVID'.
'making you' acts as a link.
(Other definitions for avid that I've seen before include "Impassioned about diva" , "passionate" , "Zealous, enthusiastic" , "Eager like diva" , "Greedily eager" .)