Swot (3,2)
I believe the answer is:
mug up
'swot' is the definition.
(I know that swot can be written as mug up)
This is the entire clue.
(Other definitions for mug up that I've seen before include "Study quickly (for, eg, an exam)" , "Swot hard" , "Learn quickly (for exam)" , "Quickly revise" , "Revise for an exam" .)