... which one drinking coffee raises? (3,2)
I believe the answer is:
mug up
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for mug up that I've seen before include "Study quickly (for, eg, an exam)" , "Study intensively" , "Make an intensive study" , "Study hard" , "Learn (subject) quickly" .)