Grump driver ultimately bundled into carriage (4)

I believe the answer is:

crab

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'grump' is the definition.
(crab is a kind of grump)

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

(Other definitions for crab that I've seen before include "The constellation Cancer" , "Shellfish with pincers" , "Stalk-eyed crustacean" , "Decapod crustacean" , "One fired from gun" .)

I've seen this clue in The Sun and The Times.

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