Clan gathered round UN champion (7)
I believe the answer is:
tribune
'champion' is the definition.
(I've seen this before)
'clan gathered round un' is the wordplay.
'clan' becomes 'tribe' (synonyms).
'gathered round' is an insertion indicator.
'tribe' going around 'un' is 'TRIBUNE'.
(Other definitions for tribune that I've seen before include "Popular demagogue" , "Champion of the people" , "Institution upholding public rights" , "Official upholder of the people's rights" , "Classic guardian?" .)