Pack, jam (5)
I believe the answer is:
stuff
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">pack</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">jam</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for stuff that I've seen before include "crowd" , "Matter" , "Substance; material" , "12 [GLUT]" , "Material; eat lots" .)