Lasting longer than Open University tutor's primary source of income (9)

I believe the answer is:

outliving

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'lasting longer' is the definition.
The definition and answer can be both to do with fundamental existence as well as being present participle verbs.
Perhaps there's an association between them I don't understand?

'open university tutor's primary source of income' is the wordplay.
'open university' becomes 'OU'.
'primary' indicates taking the first letters.
'source of income' becomes 'living' (I am not sure about this - if you are sure you should believe this answer much more).
The first letter of 'tutors' is 't'.
'ou'+'t'+'living'='OUTLIVING'

'than' is the link.

Can you help me to learn more?

(Another definition for outliving that I've seen is " Existing longer".)

I've seen this clue in The Independent.

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