Drivers' 180 (1-4)
(Other definitions for u-turn that I've seen before include "180 degrees change of direction" , "Complete reverse of car on public road" , "Complete reverse movement as by car" , "Embarrassing reversal" , "An about face, complete change of mind" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">driver's 180</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>