Naturally it rings the lagoon (5)
I believe the answer is:
atoll
'lagoon' is the definition.
The definition and answer can be both natural objects as well as being singular nouns.
Maybe there's a link between them I don't understand?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for atoll that I've seen before include "Ring-shaped coral island" , "Bikini, say" , "Coral isle" , "Coral island with central lagoon" , "Pacific coral island" .)