The French girl is allowed (5)
I believe the answer is:
legal
'is allowed' is the definition.
(I've seen this before)
'the french girl' is the wordplay.
'the french' becomes 'le'.
'girl' becomes 'gal' ('gal' can be a synonym of 'girl'**).
'le'+'gal'='LEGAL'
(Other definitions for legal that I've seen before include "within the rules" , "Allowed by law" , "Referring to the law" , "right" , "Licit" .)