Refuse to learn about comedian (6)
I believe the answer is:
sewage
'refuse' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for sewage that I've seen before include "Waste matter carried away in drains" , "Drainage waste" , "Drained waste" , "Effluence" , "Effluent" .)