Rigid, tough (5)
I believe the answer is:
stern
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">rigid</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">tough</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 stern that I've seen before include "Looking severe" , "Where sailors may be" , "Ship's rear" , "Strict, grimly serious" , "enforcing submission" .)