Polishes off yellowy drink (5,2)

I believe the answer is:

buffs up

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'yellowy drink' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'polishes off' is the wordplay.
'polishes' becomes 'buffs' (buffing is a kind of polishing).
'off' becomes 'up' (I can't explain this - if you can you should believe this answer much more).
'buffs'+'up'='BUFFS UP'

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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