Not having left of one’s own accord, as it proved (6,3)

I believe the answer is:

turned out

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'proved' is the definition.
('turn out' can be a synonym of 'prove')

I don't understand the remainder of the clue.

(Other definitions for turned out that I've seen before include "Attired" , "Dismissed" , "Ended up" , "Produced - proved - dressed" , "emptied" .)

I've seen this clue in the Evening Standard.

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