Making a comeback, group is live with online content (8)
I believe the answer is:
websites
'online content' is the definition.
(websites are online)
'making a comeback group is live with' is the wordplay.
'making a comeback' shows that the letters should be reversed in order.
'group' becomes 'set' (both can mean a collection).
'live' becomes 'be' (synonyms).
'with' becomes 'w' (abbreviation).
'set'+'is'+'be'+'w'='setisbew'
'setisbew' backwards is 'WEBSITES'.
(Other definitions for websites that I've seen before include "Internet locations" , "places to visit online" , "Be wisest among Internet data bases" , "Groups of connected pages on the World Wide Web" , "Be wisest in pursuit of www.coms" .)