Stiff, inflexible (5)
I believe the answer is:
rigid
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">stiff</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that stiff can be written as rigid)</span><br/ ><br/ >'<span class="explanation-format__original">inflexible</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that inflexible can be written as rigid)</span><br/ ><br/ ></span>
(Other definitions for rigid that I've seen before include "completely" , "not relaxing" , "Not flexible" , "Stiff and inflexible" , "starched too much?" .)