Stuffed oneself, having finished school, reportedly (9)
I believe the answer is:
overeaten
'stuffed' is the definition.
(I've seen this before)
'finished school reportedly' is the wordplay.
'finished' becomes 'over' (over can mean finished or ended).
'school' becomes 'eton' (famous UK public school).
'reportedly' shows a homophone (sound like).
'eton' sounds like 'eaten'.
'over'+'eaten'='OVEREATEN'
'oneself having' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for overeaten that I've seen before include "Scoffed too much" , "Taken in excess food" , "what Bunter had done" , "(Having) consumed too much" , "Stuffed" .)