A French beer brewed by Jacob's son (6)

I believe the answer is:

reuben

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'son' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for reuben that I've seen before include "Son of Jacob; bee run (anag.)" , "tribe" , "First son of Jacob (OT)" , "one found in the first 6 [BOOK] of the 26 [BIBLE]" , "salt beef sandwich" .)

I've seen this clue in The Globe and Mail.

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