Question about the metal barriers (5)

I believe the answer is:

grill

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'question' is the definition.
(to grill is to interrogate)

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

(Other definitions for grill that I've seen before include "pump" , "Question aggressively" , "Cook under direct heat" , "Question closely" , "Intensely question; dish" .)

I've seen this clue in the Evening Standard.

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