Describing the fish that got away? (4,8)

I believe the answer is:

sole survivor

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'describing the' is the definition.
I can't tell whether this defines the answer.

'fish that got away?' is the wordplay.
'fish' becomes 'sole' (sole is a kind of fish).
'that got away?' becomes 'survivor' (I can't explain this - if you can you should believe this answer much more).
'sole'+'survivor'='SOLE SURVIVOR'

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

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