Biography to encompass one's entire existence (8)

I believe the answer is:

lifespan

'one's entire existence' is the definition.
(duration of one's existence)

'biography to encompass' is the wordplay.
'biography' becomes 'life' (synonyms).
'to encompass' becomes 'span' (I've seen this in another clue).
'life'+'span'='LIFESPAN'

(Another definition for lifespan that I've seen is " This may be curtailed".)

I've seen this clue in The Guardian.

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