Height, elevation (8)
I believe the answer is:
altitude
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">height</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">elevation</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(altitude is a kind of elevation)</span><br/ ><br/ ></span>
(Other definitions for altitude that I've seen before include "Loftiness" , "Elevation above sea-level" , "Angular distance above the horizon" , "Elevation above sea level" , "Height above sea level" .)