Enthusiastic, prima donna making a comeback (4)
I believe the answer is:
avid
'enthusiastic' is the definition.
(similar in meaning)
'prima donna making a comeback' is the wordplay.
'prima donna' becomes 'diva' (synonyms).
'making a comeback' is a reversal indicator.
'diva' backwards is 'AVID'.
(Other definitions for avid that I've seen before include "Greedily eager" , "hungry" , "Zealous, enthusiastic" , "'Eager, zealous (4)'" , "Very keen, desirous" .)