Clear forecast is a feature of the Caribbean (5,4)
I believe the answer is:
coral reef
This might be a double definition.
'clear forecast' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'feature of the caribbean' is the second definition.
The definition and answer can be both natural objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'is a' is the link.
Can you help me to learn more?
(Another definition for coral reef that I've seen is " Navigational hazard in warm seas - real force (anag)".)