Caribbean or Mediterranean (3)
I believe the answer is:
sea
'caribbean or mediterranean' is the definition.
(I know that Caribbean Sea is a sea)
This is all the clue.
(Other definitions for sea that I've seen before include "The Med, e.g." , "Eg, Aral, Ross, Irish" , "The tide" , "Watery expanse" , "Large expanse of water" .)