____ and Nabucco are the well-known operas with prisoners' choruses (7)

I believe the answer is:

fidelio

(Other definitions for fidelio that I've seen before include "Noted work" , "Beethoven's only opera" , "18 OPERA]" , "Beethoven opera; I.e. if old (anag.)" , "Noted performance" .)

I've seen this clue in The Times.

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