Such friends as one is thick with (5)

I believe the answer is:

stout

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'such' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I don't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for stout that I've seen before include "drinks?" , "Fat; dependable" , "Corpulent" , "Inured to fatigue and hardship" , "pint" .)

I've seen this clue in the Evening Standard.

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