The most common and most likely answer to this crossword clue is the 2 plus 2 letter word TO GO
I've seen this crossword clue in The Times
T
O
G
O
More clues leading to the result TO GO
Buddy explains!
The straight part
We know that "such food should not be eaten in" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case such food should not be eaten in = to go.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.