Oratory (8)
I believe the answer is:
rhetoric
'oratory' is the definition.
(rhetoric is a kind of oratory)
This is all the clue.
(Other definitions for rhetoric that I've seen before include "Impressive or exaggerated speech as in public" , "Art of using language for persuasion" , "Eloquent and persuasive language" , "Empty words?" , "Art of effective speaking" .)