Crossword Genius

It's a choice question (5)

Ross

I believe the answer is:

which

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'question' is the definition.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for which that I've seen before include "Consumer magazine" , "Organisation giving information to consumers" , "What one?" .)

I've seen this clue in the Evening Standard.
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