Related group (6)
I believe the answer is:
family
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">related group</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 family that I've seen before include "Group of people related to one another" , "One's relations" , "Household" , "Group of relations" , "Group of related things" .)