Indulge island group (6)
I believe the answer is:
cosset
'indulge' is the definition.
(I know that indulge can be written as cosset)
'island group' is the wordplay.
'island' becomes 'cos' (Greek island).
'group' becomes 'set' (both can mean a collection).
'cos'+'set'='COSSET'
(Other definitions for cosset that I've seen before include "Pamper, coddle (6)" , "Pamper, mollycoddle" , "Protect overindulgently" , "Overindulge" , "Treat overindulgently" .)