Introduce into a famous Hall (5)

I believe the answer is:

usher

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'introduce' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for usher that I've seen before include "'The Fall of the House of -----', Edgar Allan Poe" , "may be match participant" , "Minor court official" , "Doorkeeper in parliament or 29 down" , "falling house" .)

I've seen this clue in the Evening Standard.

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