The most common and most likely answer to this crossword clue is the 7 letter word FALSIFY
I've seen this crossword clue in The Times
F
A
L
S
I
F
Y
Buddy explains!
The straight part
We know that "Cook" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cook = falsify.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.
What does FALSIFY mean?
FALSIFY verb- To alter so as to make false; to make incorrect.
- To misrepresent.
- To prove to be false.
- To counterfeit; to forge.
- To show (an item of charge inserted in an account) to be wrong.
- To baffle or escape.
- To violate; to break by falsehood.