Tied to an awful counteracting agent (8)
I believe the answer is:
antidote
'tied to an awful counteracting agent' is the definition.
(I've seen this before)
'tied to an awful' is the wordplay.
'awful' is an anagram indicator.
'tied'+'to'+'an'='tiedtoan'
'tiedtoan' with letters rearranged gives 'ANTIDOTE'.
(Other definitions for antidote that I've seen before include "Medicine to counteract poison" , "Counteracting medicine" , "Tied to an awful counteracting agent" , "Counter-agent" , "It counteracts poison" .)