Old orator blocks offensive revolutionary teacher (8)
I believe the answer is:
educator
'teacher' is the definition.
(someone who educates)
'old orator blocks offensive revolutionary' is the wordplay.
'old orator' becomes 'cato' (I can't explain this - if you can you should give a lot more credence to this answer).
'blocks' indicates putting letters inside (the inside letters form a 'blockage').
'offensive' becomes 'rude'.
'revolutionary' shows that the letters should be reversed in order.
'rude' backwards is 'edur'.
'cato' put into 'edur' is 'EDUCATOR'.
Can you help me to learn more?
(Other definitions for educator that I've seen before include "Instructor" , "Trainer, teacher" , "Teacher, lecturer" , "master, say" , "school worker" .)