The art of effective speaking (8)
I believe the answer is:
rhetoric
'the art of effective speaking' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rhetoric that I've seen before include "Torchier with language of orator" , "Art of impressive public speaking" , "High-flown speech" , "Eloquent and persuasive language" , "Hot air -- rich rote (anag)" .)