Road hauliers' favourite opera? (6)

I believe the answer is:

carmen

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'opera?' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for carmen that I've seen before include "Bizet's great Spanish opera" , "Musical from Bizet opera" , "Spanish opera by Bizet" .)

I've seen this clue in the Evening Standard.

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