Naturalness (4)
I believe the answer is:
ease
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">naturalness</span>' is the definition.<br/ ><span class="explanation-format__explanation">(ease is a kind of naturalness)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ease that I've seen before include "Lack of worry or agitation" , "Absence of effort" , "Absence of difficulty" , "Comfort and repose" , "Facilitate; repose" .)