For each opera has it (3)
I believe the answer is:
per
'for each' is the definition.
(thesaurus)
'opera has it' is the wordplay.
'has it' says the answer is hidden in the clue.
'PER' is hidden in the letters of 'opera'.
(Other definitions for per that I've seen before include "Preposition meaning for each" , "Preposition indicating by means of" , "For each or every" , "According to" .)