Hola!
It’s an American term, and not one that you’d use in UK proceedings. I am not a New York qualified lawyer, but guess that they mean that Virginia Guiffre’s case is legally flawed, and as a result she isn’t entitled to any monetary compensation (relief, in legal-speak).
It could be that he is arguing that even if the facts she has alleged are proved, for some technical reason it’s not a valid claim, or it might be because she has already (allegedly) received compensation from Epstein and in doing so agreed to take no other action against Andrew. In the latter case it’s quite possible that a court could consider that while she may have a valid case against him, she has not come to court “with clean hands herself” (yes, that’s really how they phrase it 
) as she is doing something she agreed not to do, in exchange for compensation, and so she’s not entitled to any further compensation (relief) now.