Emphasis, strain (6)
I believe the answer is:
stress
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">emphasis</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that stress is a type of emphasis)</span><br/ ><br/ >'<span class="explanation-format__original">strain</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that stress is a type of strain)</span><br/ ><br/ ></span>
(Other definitions for stress that I've seen before include "Force" , "Emphasise the pressure" , "'Worry, pressure (6)'" , "Emphasis on anxiety?" , "Emphasise the strain" .)