Insensible (4)
I believe the answer is:
numb
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">insensible</span>' is the definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for numb that I've seen before include "Unable to feel or think" , "Insensate" , "Without feeling" , "Dead" , "Without feelings" .)