Cay; eyot (5)
I believe the answer is:
islet
I believe this clue is a double definition.
'cay' is the first definition.
(I've seen this in another clue)
'eyot' is the second definition.
(I've seen this before)
(Other definitions for islet that I've seen before include "Tiles (anag.)" , "Tiles to make a small island" , "Ait or key" , "Ait or eyot" , "Detached bit of land" .)