Leave quickly without son's stuff (4)
I believe the answer is:
cram
'stuff' is the definition.
(cramming is a kind of stuffing)
'leave quickly without son's' is the wordplay.
'leave quickly' becomes 'scram' (I've seen this before).
'without' is a deletion indicator.
'scram' with 's' removed is 'CRAM'.
(Other definitions for cram that I've seen before include "Quickly learn - stuff" , "Swot (for exam)" , "Pack in or study hard" , "Stuff; study hard" , "Press together" .)