Seriousness (7)
I believe the answer is:
gravity
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">seriousness</span>' is the definition.<br/ ><span class="explanation-format__explanation">(gravity can mean seriousness or urgency)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for gravity that I've seen before include "cause producing mass movement" , "weight" , "Possible reason for dropping" , "Great seriousness" , "Pulling power" .)