The French state pound is permissible (5)
I believe the answer is:
legal
'permissible' is the definition.
(I've seen this before)
'the french state pound' is the wordplay.
'the french' becomes 'le'.
'state' becomes 'ga' (**).
'pound' becomes 'l'.
'le'+'ga'+'l'='LEGAL'
'is' is the link.
(Other definitions for legal that I've seen before include "Permitted by law" , "OK as an immigrant?" , "In accordance with statute" , "not banned" , "Conforming with the law" .)