Man treating me has poison (4,7)
I believe the answer is:
homo sapiens
'man' is the definition.
(man can refer to humanity as a whole)
'treating me has poison' is the wordplay.
'treating' indicates an anagram.
'me'+'has'+'poison'='mehaspoison'
'mehaspoison' anagrammed gives 'HOMO SAPIENS'.
(Other definitions for homo sapiens that I've seen before include "Modern humans" , "The one existing species of Man" , "Human species" , "Relative of 1 across" .)