Star in another opera (4)
I believe the answer is:
hero
'star' is the definition.
(I've seen this before)
'in another opera' is the wordplay.
'in' indicates the answer is hidden within the clue.
'HERO' can be found hidden inside 'another opera'.
(Other definitions for hero that I've seen before include "Exceptionally courageous person" , "Lamp-lighting lover" , "Valiant man" , "Man admired for courage and nobility" , "Very brave man" .)