Not all (4)
I believe the answer is:
some
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not all</span>' is the definition.<br/ ><span class="explanation-format__explanation">('some' is the opposite to 'all')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for some that I've seen before include "Undefined number" , "Several" , "An undetermined number" , "Unknown or unspecified amount or number" , "certain" .)