Crossword Genius

A question for the selectors (5)

Ross

I believe the answer is:

which

I'm a little stuck... Click here to teach me more about this clue!

'a question' is the definition.
(which is a question word)

I can't explain the rest of the clue.

Can you help me to learn more?

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

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