Circle segments
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">circle segments</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 arcs that I've seen before include "Cars (anag)" , "Bows" , "Parts of a circle" , "formations not straight" , "Curves in cars" .)