We submitted a paper more than one month ago, today we are asked to clarify one question in our paper. Does that mean the paper is just on the borderline right now?
One of the reviewers is unclear about one of the claims you are making. You could (for example) be making Claim A which you seem to have the data for, or you could be making Claim A' which is related but the fit isn't as strong.
While the reviewer could give you the benefit of the doubt (and ask you to clarify in revisions), they felt it was safer to ask ahead of time. If it was indeed Claim A', then your paper could have more serious flaws and would need more substantive revision.
I would reply as quickly as possible with the clarification and not try to over think it.