Firmly fixed or established (6)
I believe the answer is:
stable
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">firmly fixed</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">established</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for stable that I've seen before include "Firm - building for horses" , "farm building" , "Firm and dependable" , "Not likely to change" , "Firmly fixed - home for horse" .)