Grump driver ultimately bundled into carriage (4)
I believe the answer is:
crab
'grump' is the definition.
(crab is a kind of grump)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(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" .)