Scottish island returned to king whose role is telling (8)
I believe the answer is:
narrator
'whose role is telling' is the definition.
(a narrator tells a story)
'scottish island returned to king' is the wordplay.
'scottish island' becomes 'arran' (island off the coast of Scotland).
'returned' shows that the letters should be reversed in order.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'arran' back-to-front is 'narra'.
'narra'+'to'+'r'='NARRATOR'
(Other definitions for narrator that I've seen before include "Story teller" , "Commentator" , "Anecdotist" , "Soryteller" , "One who tells the tale" .)