Excessively flattering; oily (8)
I believe the answer is:
unctuous
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">excessively flattering</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">oily</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that oily can be written as unctuous)</span><br/ ><br/ ></span>
(Other definitions for unctuous that I've seen before include "Smarmy" , "Excessively flattering" , "Falsely ingratiating" , "Excessively ingratiating" , "Sycophantic - oily" .)