Serious; not drunk (5)
I believe the answer is:
sober
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">serious</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(sober can mean sensible or serious)</span><br/ ><br/ >'<span class="explanation-format__original">not drunk</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 sober that I've seen before include "Snot drunk" , "In control of one's faculties" , "Abstemious in robes" , "Serious or solemn and not drunk" , "Dry - dull" .)