Island, besmirched, also featured (2-7)
I believe the answer is:
co-starred
'featured' is the definition.
The answer and definition can be both to do with fundamental existence as well as being past participle verbs.
Perhaps they are linked in a way I don't understand?
'island besmirched' is the wordplay.
'island' becomes 'cos' (I've seen this before).
'besmirched' becomes 'tarred' (I've seen this in another clue).
'cos'+'tarred'='CO-STARRED'
'also' is the link.
Can you help me to learn more?
(Other definitions for co-starred that I've seen before include "Played the other leading role" , "Shared lead billing" .)