Elton rocks, hosting the broadcast TV event (8)
I believe the answer is:
telethon
'tv event' is the definition.
(a long TV broadcast raising money for charity)
'elton rocks hosting the broadcast' is the wordplay.
'rocks' indicates anagramming the letters.
'hosting' means one lot of letters goes inside another.
'broadcast' is an anagram indicator.
'elton' is an anagram of 'telon'.
'the' with letters rearranged gives 'eth'.
'telon' enclosing 'eth' is 'TELETHON'.
(Other definitions for telethon that I've seen before include "TV fundraiser" , "Long charity TV show" , "TV broadcast for charity" , "Lengthy broadcast for charity" , "Lengthy TV programme for charity" .)