The height of rhetoric (3)
I believe the answer is:
tor
'the height' is the definition.
(I've seen this before)
'of rhetoric' is the wordplay.
'of' says the answer is hidden in the clue.
'TOR' is hidden in the letters of 'rhetoric'.
(Other definitions for tor that I've seen before include "Dartmoor peak" , "(Dartmoor) rocky hill" , "Rot on a hill in Devon" , "A rocky hill in Devon" , "Rocky crag" .)