Study gum? (3,2)
I believe the answer is:
mug up
This clue might be a double definition.
'study' is the first definition.
(I know that mug up is a more specific form of study)
'gum?' is the second definition.
Although both the answer and definition are verbs in their base form, I cannot see how one could define the other.
Can you help me to learn more?
(Other definitions for mug up that I've seen before include "revise intensively" , "Quickly revise" , "Study hard" , "Make an intensive study" , "Learn (subject) quickly" .)