Crossword Genius

Study hard, coffee raised to lips? (3,2)

Ross

I believe the answer is:

mug up

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

'study hard' is the definition.
(I've seen this before)

'coffee raised to lips?' is the wordplay.
I cannot quite understand how this works, but
'raised' could be 'up' (similar in meaning) and 'up' is found in the answer.
The remaining letters 'mug' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for mug up that I've seen before include "Revise for an exam" , "Study; revise" , "Learn subject rapidly" , "Cram" , "Study intensively" .)

I've seen this clue in The Guardian.
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