A foul, substandard drink (3,5)

I believe the answer is:

low punch

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'a foul' is the definition.
I know nothing about this answer so I can't judge whether this works.

'substandard drink' is the wordplay.
'substandard' becomes 'low' (I can't explain this - if you can you should give a lot more credence to this answer).
'drink' becomes 'punch' (punch is an alcoholic drink).
'low'+'punch'='LOW PUNCH'

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