Produced German wine entertaining one unmarried French girl (12)
I believe the answer is:
mademoiselle
'unmarried french girl' is the definition.
'produced german wine entertaining one' is the wordplay.
'produced' becomes 'made' ('make' can be a synonym of 'produce'**).
'german wine' becomes 'moselle'.
'entertaining' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'moselle' going around 'i' is 'moiselle'.
'made'+'moiselle'='MADEMOISELLE'
(Other definitions for mademoiselle that I've seen before include "Foreign woman" , "Young lady" , "French girl; governess" , "Parisian girl" , "Young Frenchwoman" .)