Italicize or underline (6)
I believe the answer is:
stress
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">italicize</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">underline</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that underline is a more specific form of the action stress)</span><br/ ><br/ ></span>
(Other definitions for stress that I've seen before include "Put weight on" , "what causes tension" , "why off work?" , "Draw attention to" , "nervous tension" .)