Its sting is not in the tail (6)

I believe the answer is:

nettle

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'tail' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for nettle that I've seen before include "anger?" , "Plant to irritate" , "Annoy - stinger" , "Irritate, annoy" , "Upset" .)

I've seen this clue in The Irish News.

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