Unpleasantly suave (6)
I believe the answer is:
smarmy
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unpleasantly suave</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for smarmy that I've seen before include "Bootlicking" , "Excessively flattering (R, not L)" , "Oily" , "Excessively ingratiating" , "Fawning" .)