Lock or ringlet (5)
I believe the answer is:
tress
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">lock</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(both can mean a piece of hair)</span><br/ ><br/ >'<span class="explanation-format__original">ringlet</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for tress that I've seen before include "Long piece of hair" , "Curl - lock" , "is a bit of a shock" , "Braid of hair" , "Switch" .)