Not as high (5)
I believe the answer is:
lower
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not as high</span>' is the definition.<br/ ><span class="explanation-format__explanation">('low' can be the opposite of 'high' so perhaps 'lower' is reasonable for 'not as high')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for lower that I've seen before include "of lesser status" , "Let down; frown" , "where are trousers in relation?" , "Cow" , "put down" .)