Move around with new toxin (5)
I believe the answer is:
venom
'toxin' is the definition.
(I know that venom is a type of animal toxin)
'move around with new' is the wordplay.
'around with' indicates an anagram.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'move' with its letters anagrammed with 'n' makes 'VENOM'.
(Other definitions for venom that I've seen before include "Poisonous secretion" , "bitterness" , "Spite: toxin" , "Toxic substance" , "Snake's poison" .)