Drink for sides on bench? Water! (4)

I believe the answer is:

beer

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'drink' is the definition.
(beer is a kind of drink)

I cannot understand how the rest of the clue works.

(Other definitions for beer that I've seen before include "Ale, lager etc" , "It may be 13 across-ed!" , "Fermented malt and hops" , "Drink with a head" , "See 4 down" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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