Personal belongings fill up (5)
I believe the answer is:
stuff
I believe this clue is a triple definition!
'personal' is the first definition.
(thesaurus)
'belongings' is the second definition.
(I've seen this in another clue)
'fill up' is the third definition.
(I know that stuff is a more specific form of fill up)
(Other definitions for stuff that I've seen before include "12 [GLUT]" , "Jam" , "Material - things" , "set with unspecified ingredients" , "Miscellaneous objects" .)