cut him some slack

Theodore Boone kid lawyerを読んでいます。
Yet, a promise is a promise, and Theo had given his word to Julio and to his cousin that he would keep their secret safe. What if he didn’t? What if he marched into Judge Gantry’s chambers first thing in the morning and flung the gloves on his desk and told everything? The cousin would be toast. He would be chased down by Jack Hogan and the police and hauled into custody. His testimony would save the day for the prosecution. A mistrial would be declared. A new trial would be scheduled. It would be all over the newspapers and television. The cousin would be the hero, but he would also be locked up as an illegal immigrant.
But couldn’t he, the cousin, make a deal with the police and prosecutors? Wouldn’t they cut him some slack because they needed him?
"slack" に緩みの意味があり、ハワイアンミュージックで "slack guitar" と言うチューニングがあるのも知っていますが、この "cut him some slack" は慣用句の様です。辞書を見ます。
・Cambridge English Dictionary: to not judge someone as severely as you usually would because they are having problems at the present time: Andrew's late again." "Cut him some slack - his wife just had a baby.
・Cambridge Dictionary of American Idioms: cut somebody some slack (spoken): to give someone additional freedom I'm going to cut you some slack. Because it's the last day of classes, we don't have to talk anything serious today. If you and your kids don't agree about their futures, cut them some slack - explain your views, but don't try to force them to agree.
・Dictionary.com: To make allowances for someone, and not treat a failure severely He's the new kid on the block and doesn't know the way we do things around here yet. Cut him some slack and let him learn from this.
なるほど、大目に見る感じですね。