Deadly nightshade (10)
I believe the answer is:
belladonna
'deadly nightshade' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for belladonna that I've seen before include "brought a sparkle to the eye" , "Drug made from deadly nightshade" , "plant" , "Boy in Lebanon destroyed" , "Deadly nightshade or atropine" .)