Put one's foot down impressively (5)

I believe the answer is:

stamp

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'put one's foot down' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for stamp that I've seen before include "Mark of approval" , "Impress (a pattern)" , "What to put on 7 before putting in 15" , "put one's foot down hard" , "Tread noisily" .)

I've seen this clue in the Evening Standard.

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