As wind can rise (7)
I believe the answer is:
arsenic
'as' is the definition.
(As is the chemical symbol for arsenic)
'wind can rise' is the wordplay.
'wind' is an anagram indicator.
'can'+'rise'='canrise'
'canrise' with letters rearranged gives 'ARSENIC'.
(Other definitions for arsenic that I've seen before include "Ratsbane" , "Powerful poison" , "Poisons in scare" , "Poison found in races" , "Can rise result from poison?" .)