"Smooth Operator" singer (4)
I believe the answer is:
sade
'smooth operator singer' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sade that I've seen before include "The Marquis de . . . . was noted for cruelty" , "Marquis de ..., famous for taking pleasure in pain" , "Jazz-pop group" , "letter from Israel?" , "Hebrew character" .)