Crossword Genius

Raise drink! Another drink! A lot of drinking (4-2)

Ross

I believe the answer is:

piss-up

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'a lot of drinking' is the definition.
(session of excessive drinking)

'raise drink another drink' is the wordplay.
'raise' says the letters should be written in reverse.
'drink' becomes 'sip' (sipping is a kind of drinking).
'another drink' becomes 'sup' (to sup is to drink. I am not sure about the 'another' bit.).
'sip' in reverse letter order is 'pis'.
'pis'+'sup'='PISS-UP'

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I've seen this clue in The Guardian.
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