It forms a ring in more ways than one (5)
I believe the answer is:
atoll
'it forms a' is the definition.
The definition suggests a singular noun which matches the answer.
'ring in more ways than one' is the wordplay.
I cannot quite understand how this works, but
'ring' could be 'toll' (a bell tolls) and 'toll' is found in the answer.
'one' could be 'a' (a thing is one thing) and 'a' is located in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for atoll that I've seen before include "land threatened by rising sea levels" , "Coral isle" , "Coral island with central lagoon" , "Ring-shaped coral island" , "Land around a lagoon, such as Bikini" .)