Start to smoke joints audibly, showing sign of irritation (6)

I believe the answer is:

sneeze

'sign of irritation' is the definition.

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

(Other definitions for sneeze that I've seen before include "Minor bodily explosion" , "Go a-tishoo!" , "Precursor to "bless you"" , "Nasal eruption from common cold" , "Explosive nasal action" .)

I've seen this clue in The Guardian.

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