Cram; matter (5)
I believe the answer is:
stuff
This clue is a double definition.
'cram' is the first definition.
(I know this)
'matter' is the second definition.
(stuff is a kind of matter)
(Other definitions for stuff that I've seen before include "facts" , "12 [GLUT]" , "Miscellaneous objects" , "Matter" , "Material; eat lots" .)