Rambling rector and his endless oratory (8)
I believe the answer is:
rhetoric
'oratory' is the definition.
(rhetoric is a kind of oratory)
'rambling rector and his endless' is the wordplay.
'rambling' indicates anagramming the letters.
'and' says to put letters next to each other.
'endless' means to remove the last letter.
'his' with its final letter taken off is 'hi'.
'rector' put after 'hi' is 'hirector'.
'hirector' with letters rearranged gives 'RHETORIC'.
(Other definitions for rhetoric that I've seen before include "Grandiloquence, oratory" , "High-flown language as for speeches" , "Eloquent and persuasive language" , "Torchier kind of colourful speech" , "Vague talk and empty promises" .)