Going on at entertaining buffoon endlessly (5)
I believe the answer is:
afoot
'going on' is the definition.
(I've seen this in another clue)
'at entertaining buffoon endlessly' is the wordplay.
'entertaining' is an insertion indicator (inviting in, as for dinner).
'buffoon endlessly' becomes 'foo' (I can't explain this - if you can you should give a lot more credence to this answer).
'at' placed around 'foo' is 'AFOOT'.
Can you help me to learn more?
(Other definitions for afoot that I've seen before include "Brewing" , "Currently in progress" , "In the pipeline" , "Progressing, in operation - like Sherlock Holmes's game" , "Going on" .)