Crossword Genius

Better drink, consuming last of lager before idiot (7)

Ross

I believe the answer is:

surpass

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

'better' is the definition.
(thesaurus)

'drink consuming last of lager before idiot' is the wordplay.
I cannot quite understand how this works, but
'idiot' could be 'ass' (I've seen this before) and 'ass' is found within the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for surpass that I've seen before include "Excel" , "Exceed" , "Go one better" , "supply best" , "Outdo" .)

I've seen this clue in The Telegraph.
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