Contrarily put on Grease though opera's wanted (7)
I believe the answer is:
fidelio
'contrarily put' is the definition.
The definition suggests a singular noun which matches the answer.
I cannot understand how the rest of the clue works.
(Other definitions for fidelio that I've seen before include "Noted performance" , "18 OPERA]" , "Noted work" , "Beethoven opera; I.e. if old (anag.)" , "Beethoven's only opera" .)