Not quickly (6)
I believe the answer is:
slowly
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not quickly</span>' is the definition.<br/ ><span class="explanation-format__explanation">(slow as opposed to quick)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for slowly that I've seen before include "Going at a low speed" , "Little by little" , "Not quickly" , "At a leisurely pace" , "Gradually" .)