Sounds like key opening (6)
I believe the answer is:
eyelet
'opening' is the definition.
(hole for putting a shoelace through)
'sounds like key' is the wordplay.
'sounds like' shows a homophone (sound like).
'key' becomes 'islet' (both can mean a small island).
'islet' is a homophone of 'EYELET'.
(Other definitions for eyelet that I've seen before include "Hole for a lace or cord" , "Small hole to pass lace through" , "Hole in needle through which thread passes" , "A lace is passed through it" , "Loophole" .)