A massage on a Caribbean island (5)
I believe the answer is:
aruba
'caribbean island' is the definition.
(I've seen this before)
'a massage on a' is the wordplay.
'massage' becomes 'rub' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'a'+'rub'+'a'='ARUBA'
(Other definitions for aruba that I've seen before include "Island resort in the Dutch Antilles" , "Caribbean island" .)