Sharp twist (4)
I believe the answer is:
kink
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sharp twist</span>' is the definition.<br/ ><span class="explanation-format__explanation">(a kink is a twist or knot)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for kink that I've seen before include "Mental quirk" , "Constricting bend in pipe" , "Quirk of behaviour" , "Idiosyncrasy - sharp bend" , "Sharp bend (in a wire) - quirk" .)