Very keen pupil pulls up (4)
I believe the answer is:
swot
'very keen pupil' is the definition.
(I've seen this before)
'pulls up' is the wordplay.
'pulls' becomes 'tows' (tow is a kind of pull).
'up' is a reversal indicator (in down clue: letters go upwards).
'tows' in reverse letter order is 'SWOT'.
(Other definitions for swot that I've seen before include "Very diligent student" , "Nerd" , "Cram for exam" , "One studying a lot" , "Very studious person" .)