Arthurian island (6)
I believe the answer is:
avalon
'arthurian island' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for avalon that I've seen before include "Morgan le Fay's isle" , "Celtic island of the blessed" , "Where King Arthur's body was brought" , "Resting place of King Arthur" , "King Arthur's burial place" .)