Potentially painful growth to irritate (6)

I believe the answer is:

nettle

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'to irritate' is the definition.
(synonyms)

I can't explain the remainder of the clue.

(Other definitions for nettle that I've seen before include "Annoy; common weed" , "Grasp it firmly and it will not sting" , "To be annoying" , "Clasp it firmly and it will not sting" , "urticaceous plant" .)

I've seen this clue in The Mirror.

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