Smug smile (5)
I believe the answer is:
smirk
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">smug smile</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for smirk that I've seen before include "Complacent smile" , "Smug look" , "Self-satisfied smile" , "Smug smile" , "Derisive smile" .)