New York island is well isolated in part (5)
I believe the answer is:
ellis
'new york island' is the definition.
(I've seen this in another clue)
'is well isolated in part' is the wordplay.
'in part' says the answer is hidden in the clue.
'ELLIS' is hidden in the letters of 'is well isolated'.
(Other definitions for ellis that I've seen before include "- - Peters (novelist)" , "island close to New York" , "expert in sexual psychology" , "-- Bell, Bronte pen name" , "who wrote sexy books?" .)