Vigilance (9)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vigilance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for alertness that I've seen before include "Watchful attitude" , "It's needed to respond quickly to danger" , "Showing attentive nature" , "Watchful state" , "Wakeful characteristic" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vigilance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that vigilance can be written as watchfulness)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Another definition for watchfulness that I've seen is " Vigilance".)