Stuff to study for an exam (4)
I believe the answer is:
cram
This clue is a double definition.
'stuff' is the first definition.
(cramming is a kind of stuffing)
'study for an exam' is the second definition.
(I've seen this before)
'to' is the link.
(Other definitions for cram that I've seen before include "Swot (for exam)" , "A crush" , "Stuff; study hard" , "Greedily eat" , "Quickly learn - stuff" .)