急求各位英语高手帮忙解答下这句英语

its指代前面的the stream
有些名词后可以直接接副词，比如说，
the way 后面可以接副词，across 就是副词，横跨，跨过的意思.
我觉得你有个词写错了，应该是tent.
原句是： It was raining heavily and they found that a stream had formed in the field. The stream wound its way across the field and then flowed right under their tent!
大概的意思就是:
雨下得很大,在地面上形成了一条小溪，这条小溪流流过了田野，笔直的流向了他们的帐篷。

注意断句就不难理解了。
wound its way/across the field，这里主要涉及到across的用法，很明显不是你说的固定搭配。
注意区别于through、over等词。

是穿过的意思

例句:
The stream wound its way across the field and then flowed with under their tent!

那小溪弯弯曲曲穿过田野，然后正好从他们的帐篷下流过去。