Poison abused in scare (7)
I believe the answer is:
arsenic
'poison' is the definition.
(arsenic can be used as a poison)
'abused in scare' is the wordplay.
'abused' is an anagram indicator.
'in'+'scare'='inscare'
'inscare' with letters rearranged gives 'ARSENIC'.
(Other definitions for arsenic that I've seen before include "Can rise result from poison?" , "Famous stage comedy ''. . . . . . . and Old Lace''" , "Ratsbane" , "Poison found in races" , "Poisons in scare" .)