Carriage appears to have been upset (5)

I believe the answer is:

sulky

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'carriage' is the definition.
(thesaurus)

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

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

I've seen this clue in The Globe and Mail.

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