Caribbean or Aegean (3)
I believe the answer is:
sea
'caribbean or aegean' 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." , "70% of the earth's surface" , "Cod's home?" , "E.g Aral or Weddell" , "North, say" .)