Do nothing but watch what a generous drinker will do? (5,6)

I believe the answer is:

stand around

I'm a little stuck... Click here to teach me more about this clue!

'do nothing' is the definition.
(thesaurus)

'watch what a generous drinker will do?' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is found in the answer.
This explanation may well be incorrect...

'but' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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