Social division (5)
I believe the answer is:
tribe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">social division</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 tribe that I've seen before include "social set" , "Race" , "Group of related families" , "Clannish group" , "Division of, eg, North American natives" .)