loose rein
noun
in sing.
1- a manner of riding in which the reins are held slackly, so that the horse is able to relax and stretch放松缰绳（指一种骑马方法, 能使马肌肉和四肢放松）：
on a loose rein, he ran better.
放松了缰绳, 马儿跑得来劲了。
1.1
- a lack of strict control in organizing something缺乏严格管理：
he ran foreign affairs on a loose rein.
他管理外交工作不严格。