Around Uist's edge, catch isle's sea creatures (7)
I believe the answer is:
nautili
'sea creatures' is the definition.
(I've seen this before)
'around uist's edge catch isle's' is the wordplay.
'around' means one lot of letters goes inside another.
'edge' suggests removing the centre (I've seen 'edging' mean this (edging means the letters on the edges)).
'catch' becomes 'nail' (I've seen this before).
'isle' becomes 'i'.
'uist' with its centre taken out is 'ut'.
'ut' put into 'nail' is 'nautil'.
'nautil'+'i'='NAUTILI'
(Other definitions for nautili that I've seen before include "creatures in the sea" , "marine life" , "Cephalopod molluscs" .)