Article changes diet to remedy (8)
I believe the answer is:
antidote
'remedy' is the definition.
(I know that antidote is a type of remedy)
'article changes diet to' is the wordplay.
'article' becomes 'an' (indefinite article).
'changes' indicates an anagram.
'diet'+'to'='dietto'
'dietto' with letters rearranged gives 'tidote'.
'an'+'tidote'='ANTIDOTE'
(Other definitions for antidote that I've seen before include "Counter to a poison" , "Medicine to counteract poison" , "Counter-measure" , "It neutralises poison" , "Counterpoison" .)