One of three born together (7)
I believe the answer is:
triplet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">one of three born together</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for triplet that I've seen before include "Set of three things" , "Handful of notes" , "One of three born at the same time" , "One of several arriving together" , "One of a set of three" .)