Overly suave (4)
I believe the answer is:
oily
'overly suave' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oily that I've seen before include "Smoothly ingratiating" , "Unctuous" , "Smooth; like lubricant" , "Greasy - obsequious" , "Viscous" .)