Ignoble - HQ (4)
I believe the answer is:
base
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">ignoble</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">hq</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(HQ is headquarters)</span><br/ ><br/ ></span>
(Other definitions for base that I've seen before include "Foot; ignoble" , "Plinth" , "Foundation; counterfeit" , "floor" , "Bottom support" .)