Some fictitious island to hold dear (8)
I believe the answer is:
treasure
'hold dear' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for treasure that I've seen before include "Robert Louis Stevenson novel" , "Accumulated wealth, might be buried" , "Jewel hoard" , "Accumulated wealth, could be buried" , "someone valued" .)