Not bottom (3)
I believe the answer is:
top
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not bottom</span>' is the definition.<br/ ><span class="explanation-format__explanation">('top' is the opposite to 'bottom')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for top that I've seen before include "SECOND PART OF 10 ACROSS" , "Summit, peak" , "Peak; child's toy" , "Acme or apex" , "cap and > sweater" .)