Catherine made history as a survivor (4)

I believe the answer is:

parr

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'survivor' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps you can see an association between them that I don't see?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for parr that I've seen before include "Wife surviving" , "Young salmon; Queen Catherine ---" , "Henry VIII's sixth queen" , "Fish" , "old trout?" .)

I've seen this clue in the Evening Standard.

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