Weapon a cavalryman will know how to handle? (4)

I believe the answer is:

colt

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'weapon' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

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

Can you help me to learn more?

(Other definitions for colt that I've seen before include "Young Arab maybe" , "Youngster" , "Type of American revolver" , "H [HORSE]" , "Mount" .)

I've seen this clue in the Evening Standard.

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