Average salmon caught as menu item? (3,3,3,6)

I believe the answer is:

par for the course

'average' is the definition.
(par for the course means average or expected)

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

(Other definitions for par for the course that I've seen before include "72?" , "Typical" , "Standard" , "Normal" , "achievement that seems full of holes?" .)

I've seen this clue in The Guardian.

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