Food product mistakenly made (4)

I believe the answer is:

hash

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'food' is the definition.
(hash is a kind of food)

I don't understand the rest of the clue.

(Other definitions for hash that I've seen before include "Jumble or mixture for shah" , "Meat dish or hallucinogen" , "preparation that's nothing new" , "Reheated dish" , "Mess; symbol" .)

I've seen this clue in the Evening Standard.

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