Poison remedy includes stripped bark (6)
I believe the answer is:
curare
'poison' is the definition.
(I know that curare is a type of phytotoxin)
'remedy includes stripped bark' is the wordplay.
'remedy' becomes 'cure' (synonyms).
'includes' is an insertion indicator.
'stripped' indicates the central letters (outside letters removed).
The centre of 'bark' is 'ar'.
'cure' placed around 'ar' is 'CURARE'.
(Other definitions for curare that I've seen before include "Arrow poison" , "Poison used on darts" , "Poison applied to darts" , "Poison put on arrows" , "Paralysing plant poison" .)