Dangerous poison (5)
I believe the answer is:
ricin
'dangerous poison' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ricin that I've seen before include "bioweapon" , "Highly-toxic poison" , "Toxic protein from castor oil plant seeds" , "Highly toxic plant protein" , "Poison found in caster-oil beans" .)