Crowd supported end to fine, lively celebration (8)
I believe the answer is:
jamboree
'lively celebration' is the definition.
(I've seen this before)
'crowd supported end' is the wordplay.
'crowd' becomes 'jam' (jam is a kind of crowd).
'supported end' becomes 'boree' (I can't explain this - if you can you should believe this answer much more).
'jam'+'boree'='JAMBOREE'
'to fine' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for jamboree that I've seen before include "Rally of Guides or Scouts" , "'Gala get-together, of scouts say (8)'" , "where lad of 14 [BOY SCOUT] meets more troops?" , "Lavish celebration" , "Large and lively party" .)