Kingdoms (6)
I believe the answer is:
realms
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">kingdoms</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for realms that I've seen before include "Kingdoms, domains" , "Kingdoms, or fields of activity" , "regions" , "areas of interest" , "Fields of activity or interest - sound monarchical" .)