Closed circuit (4)
I believe the answer is:
loop
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">closed circuit</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 loop that I've seen before include "Endless film strip" , "Noose" , "Aerobatics manoeuvre" , "ring road, say" , "Aircraft manoeuvre; encircle" .)