The most common and most likely answer to this crossword clue is the 5 letter word AVERS
I've seen this crossword clue in The Guardian
A
V
E
R
S
More clues leading to the result AVERS
- States opposed omitting conclusion
- States endlessly unwilling
- Mostly hostile states
- Declares a piece of poetry ‘inadequate’
- States reluctant to drop English, finally
- States unsympathetic after English exit
- Makes assertions about leaving speleologists
- Declares a piece of poetry endless
- Declares a verse is shortened
- Declares a piece of poetry interminably
Buddy explains!

The straight part
We know that "States" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case states = avers.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 AVERS mean?
AVERS verb- To assert the truth of, to affirm with confidence; to declare in a positive manner.
- To prove or justify a plea.
- To avouch, prove, or verify; to offer to verify.