Simper (5)
I believe the answer is:
smirk
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">simper</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that simper can be written as smirk)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for smirk that I've seen before include "Leer" , "Complacent smile" , "Show self-complacent satisfaction" , "Smug look" , "Smile scornfully" .)