Trio or triad (5)
I believe the answer is:
three
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">trio</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that trio can be written as three)</span><br/ ><br/ >'<span class="explanation-format__original">triad</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that triad can be written as three)</span><br/ ><br/ ></span>
(Other definitions for three that I've seen before include "Number of feet in a yard" , "III" , "Number of strikes before you're out" , "Prime number" , "Amount in a trio" .)