Crossword Genius

Poisonous plant made nark convulsive (8)

Ross

I believe the answer is:

mandrake

I'm a little stuck... Click here to teach me more about this clue!

'poisonous plant' is the definition.
(plant of the nightshade family)

'made nark convulsive' is the wordplay.
'made nark' anagrams to 'MANDRAKE'.
But, I am unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for mandrake that I've seen before include "Poisonous plant or cartoon magician" , "Plant once believed to shriek when pulled up" , "Root used in medicine" , "Poisonous plant with large forked root" , "Herbal root" .)

I've seen this clue in The Guardian.
Want a hint initially instead of a full solution? Install my app