A very enthusiastic rising singer (4)
I believe the answer is:
diva
'singer' is the definition.
(diva is a kind of singer)
'a very enthusiastic rising' is the wordplay.
'a very enthusiastic' becomes 'avid' (I've seen this before).
'rising' is a reversal indicator (going up in a down clue).
'avid' written backwards gives 'DIVA'.
(Other definitions for diva that I've seen before include "Celebrated female operatic star" , "Grand female singer" , "Top opera singer" , "Successful lady" , "demanding woman" .)