As a drinker, what's yours? (6)

I believe the answer is:

poison

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'as' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps you can see a link between them that I don't see?

I can't explain the rest of the clue.

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(Other definitions for poison that I've seen before include "Eg, strychnine" , "Corrupt" , "Dangerous substance" , "Eg, toxin" , "Toxic substance" .)

I've seen this clue in the Evening Standard.

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