Impermanence convert ultimately found in virtue (9)

I believe the answer is:

mortality

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'impermanence' is the definition.
(mortality is a kind of impermanence)

'convert ultimately found in virtue' is the wordplay.
'convert ultimately' becomes 't' (I can't explain this - if you can you should believe this answer much more).
'found in' indicates putting letters inside.
'virtue' becomes 'morality' (I've seen this before).
't' placed inside 'morality' is 'MORTALITY'.

Can you help me to learn more?

(Other definitions for mortality that I've seen before include "Death" , "State of humanity" .)

I've seen this clue in The Telegraph.

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