Fourth-most-produced grain worldwide (after corn, wheat and rice) (6)

I believe the answer is:

barley

(Other definitions for barley that I've seen before include "The grain may make you bleary" , "A grass; its wine a beer" , "Grain used in making beer" , "Grain used in brewing" , "Cereal used in beer" .)

I've seen this clue in The New York Times.

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