Grumpy carriage (5)

I believe the answer is:

sulky

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This clue could be a double definition.

'grumpy' is the first definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I can't see?

'carriage' is the second definition.
(thesaurus)

Can you help me to learn more?

(Other definitions for sulky that I've seen before include "Sullen" , "Morose" , "Moody" , "Petulant" .)

I've seen this clue in the Sydney Morning Herald.

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