The draught is water (7)

I believe the answer is:

current

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'the draught' is the definition.
(thesaurus)

I don't understand the remainder of the clue.

(Other definitions for current that I've seen before include "Contemporary" , "Popular" , "Flow of electricity" , "Electrical flow" , "Source of power" .)

I've seen this clue in the Evening Standard.

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