Description of an eternity ring? (5-6)

I think it could be either:

Which length description are you looking for?:

5-6

never-ending

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'description of' is the definition.
The answer and definition are not the same part of speech.

'eternity ring?' is the wordplay.
I cannot quite see how this works, but
'eternity' could be 'ever' (I've seen this before) and 'ever' is located in the answer.
'ring?' could be 'ding' (dinging is a kind of ringing) and 'ding' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

'an' acts as a link.

Can you help me to learn more?

(Other definitions for never-ending that I've seen before include "Everlasting" , "Eternal" , "Ceaseless" , "Interminable" , "Not finishing" .)

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

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