The most common and most likely answer to this crossword clue is the 5 letter word NIXES
N
I
X
E
S
Buddy explains!
The straight part
We know that "Says no to" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case says no to = nixes.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 NIXES mean?
NIXES verb- To make something become nothing; to reject or cancel.
- To destroy or eradicate.
- Nothing