Inflexible, unyielding (5)
I believe the answer is:
rigid
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">inflexible</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">unyielding</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for rigid that I've seen before include "stern" , "Hard" , "Unable to bend" , "strict" , "Incapable of or resistant to bending" .)