Poison distributed in scare (7)
I believe the answer is:
arsenic
'poison' is the definition.
(thesaurus)
'distributed in scare' is the wordplay.
'distributed' is an anagram indicator.
'in'+'scare'='inscare'
'inscare' with letters rearranged gives 'ARSENIC'.
(Other definitions for arsenic that I've seen before include "-- and Old Lace (play)" , "Poisons in scare" , "Element with many poisonous compounds" , ", it goes with old lace" , "Ratsbane" .)