Hurry up and start climbing the ladder! (4,2,2)

I believe the answer is:

step on it

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

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

(Other definitions for step on it that I've seen before include "Hurry! - set point (anag)" , "So join the escalator" , "to flatten an insect?" , "Get a move on!" , "Be quick" .)

I've seen this clue in the Evening Standard.

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