Belief essential to opera stars? (5)
I believe the answer is:
rasta
'belief' is the definition.
(Rastafarianism is a religion)
'essential to opera stars?' is the wordplay.
'essential to' indicates a hidden word (I've seen this in other clues).
'RASTA' can be found hidden inside 'opera stars'.
(Other definitions for rasta that I've seen before include "Religious type" , "black believer" , "Religious adherent" , "One dreaded" , "Member of religious movement originating in Jamaica" .)