at a loose end 无所事事，无事可做

【例句】
Adolescents are most likely to get into trouble when they're at a loose end.
青少年无所事事的时候最容易惹出麻烦来。

Come and see us, if you're at a loose end.
你要是闲着无事就来我们这儿坐坐吧。