Wood entirely in foil (9)
I believe the answer is:
forestall
'foil' is the definition.
'wood entirely' is the wordplay.
'wood' becomes 'forest' (synonyms).
'entirely' becomes 'all' (I've seen this before).
'forest'+'all'='FORESTALL'
'in' is the link.
(Other definitions for forestall that I've seen before include "Obstruct by taking advance action" , "Take action before" , "Hinder by anticipation" , "Arrive first" , "Thwart" .)