Ring an agent back at Covent Garden? (5)

I believe the answer is:

opera

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But I can't explain it at all! Could you help me understand?

(Other definitions for opera that I've seen before include "Eg, La traviata" , "Tosca, for example" , "some theatrics" , "Met show?" , "Musical dramatic work" .)

I've seen this clue in The Globe and Mail.

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