Key point (4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">key point</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for crux that I've seen before include "puzzle" , "Essence or gist" , "Nub" , "The most important thing" , "Essential point in the matter or problem" .)