French good to guard Italian wine in fortress (7)
I believe the answer is:
bastion
'fortress' is the definition.
(I've seen this before)
'french good to guard italian wine' is the wordplay.
'french good' becomes 'bon' ('good' in French).
'to guard' is an insertion indicator.
'italian wine' becomes 'asti' (Asti is a type of Italian wine).
'bon' enclosing 'asti' is 'BASTION'.
'in' is the link.
(Other definitions for bastion that I've seen before include "Obtains in fortified place or stronghold" , "Projecting part of a fortification" , "A projecting fortification to increase angle of fire" , "fortress" , "staunch supporter" .)