Without a hitch (8)
I believe the answer is:
smoothly
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">without a hitch</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for smoothly that I've seen before include "Evenly or with no difficulty" , "Evenly, with no problems or difficulties" , "Evenly, regularly" .)