Ultimate aim of pub game, large drink (6)

I believe the answer is:

double

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'large drink' is the definition.
(drink with a double shot)

I can't explain the remainder of the clue.

(Other definitions for double that I've seen before include "- - -u, (w)" , "Score of forty with one dart, perhaps?" , "Twice - bent over - run" , "With two equal parts" , "Multiply by two" .)

I've seen this clue in The Guardian.

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