The most common and most likely answer to this crossword clue is the 7 letter word ALLEGES
I've seen this crossword clue in Independent
A
L
L
E
G
E
S
Buddy explains!

The straight part
We know that "claims" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case claims = alleges.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 ALLEGES mean?
ALLEGES verb- To state under oath, to plead.
- To cite or quote an author or his work for or against.
- To adduce (something) as a reason, excuse, support etc.
- To make a claim as justification or proof; to make an assertion without proof.
- To lighten, diminish.