Quick to become irritable (6)

I believe the answer is:

snappy

I believe this is a double definition.

'quick' is the first definition.
(thesaurus)

'irritable' is the second definition.
(thesaurus)

'to become' is the link.

(Other definitions for snappy that I've seen before include "Smart - lively" , "bad tempered" , "edgy" , "Quick and energetic" , "Elegant" .)

I've seen this clue in the Evening Standard.

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