23 across
Smooth
talker
on
X,
say
(8)
Smooth talker on X, say (8)
hints
0
checks
0
hints
The whole clue is the definition (& lit or double definition).
How the clue works
The first definition Smooth talker refers to a smooth operator, someone glib and persuasive. The second definition X, say points to X being an example of a mathematical operator (the multiplication sign), with 'say' signalling 'for example', and 'on' serving as a link word.