Remedy for poison (8)
I believe the answer is:
antidote
'remedy for poison' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for antidote that I've seen before include "Counterpoison" , "Medicine countering a poison" , "Donate it to anti-poison agent" , "Counteracting medicine" , "Counteracting remedy" .)