Descriptive of an eternity ring? (7)

I believe the answer is:

endless

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'descriptive' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for endless that I've seen before include "Unceasing" , "Eternal or interminable" , "Havin no limit" , "Sister of Aaron (Exodus)" , "permanent" .)

I've seen this clue in The Guardian, The Globe and Mail and The Telegraph.

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