A cheap drink (5)

I believe the answer is:

water

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'drink' is the definition.
(thesaurus)

I can't explain the rest of the clue.

(Other definitions for water that I've seen before include "Earth, air, fire partner" , "Commonplace drink" , "Common liquid" , "Compound of hydrogen and oxygen" , "Essential liquid" .)

I've seen this clue in the Evening Standard.

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