How might one kill a creepy-crawly? Be quick! (4,2,2)

I believe the answer is:

step on it

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'quick' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for step on it that I've seen before include "Be quick" , "Informally, hurry or drive faster" , "How might one kill an ant" , "improve rate of advance" , "Get a move on!" .)

I've seen this clue in The Telegraph.

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