Part of the Scillies, eastern half redeveloped (4)
I believe the answer is:
isle
'part of' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'scillies eastern half redeveloped' is the wordplay.
'eastern half' suggests halving the letters (letters on the right or 'east').
'redeveloped' indicates anagramming the letters.
'scillies' cut in half is 'lies'.
'lies' anagrammed gives 'ISLE'.
'the' acts as a link.
(Other definitions for isle that I've seen before include "Capri or Man, perhaps?" , "Small island" , "Piece of land in water" , "Lies (anag)" , "See 10 Down" .)