Insincere charm (5)
I believe the answer is:
smarm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">insincere charm</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for smarm that I've seen before include "oil" , "Superficially ingratiating behaviour" , "Fawning" , "Obsequious flattery" , "Smooth talking" .)