Sounds like steak and fish starters for evening dinner sold down the river (8)

I believe the answer is:

betrayed

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'sold down the river' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for betrayed that I've seen before include "Gave away" , "Unintentionally showed" , "Was unfaithful" , "Delivered to an enemy by treachery" , "Broke one's promise" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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