Inspiration seen in opera, 'Tosca' (5)
I believe the answer is:
erato
'inspiration' is the definition.
(one of the muses in Greek mythology)
'in opera tosca' is the wordplay.
'in' indicates a hidden word.
'ERATO' is hidden in the letters of 'opera tosca'.
'seen' acts as a link.
(Other definitions for erato that I've seen before include "Inspiring female" , "Source of artistic inspiration" , "Lyric poetry's muse" , "Greek muse - orate (anag)" , "Arts patron" .)