Organised event to support British actor (6)
I believe the answer is:
brando
'actor' is the definition.
(I've seen this before)
'organised event to support british' is the wordplay.
'organised' becomes 'ran' (I've seen this before).
'event' becomes 'do' (do is a kind of event).
'to support' means one lot of letters go next to another.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'ran'+'do'='rando'
'rando' after 'b' is 'BRANDO'.
(Other definitions for brando that I've seen before include "Marlon . . . . . ., star of ''On The Waterfront'' (6)" , "actor in 4 26 21 [A STREETCAR NAMED DESIRE]" , "heart-throb" , "Marlon --, film actor" , "'The Godfather'?" .)