Boasted about how French reportedly classify their wines (3)
I believe the answer is:
cru
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for cru that I've seen before include "Vineyard or group of them in France" , "(Quality) vineyard; sounds like ship's men" , "Growth place of a French wine" , "French vineyard (and the wine from it)" , "Grounds for eg red" .)