Driving them before it...

[suprunp]

"In a few days small white clouds started their winter parade, trooping across the sky, soft and chubby, long, languorous, and unkempt, or small and crisp as feathers, and driving them before it, like an ill-assorted flock of sheep, would come the wind." (My Family and Other Animals by Gerald Durrell)

Q: What does it stand for in this sentence?

Thanks.

[Raymott]

"In a few days small white clouds started their winter parade, trooping across the sky, soft and chubby, long, languorous, and unkempt, or small and crisp as feathers, and driving them before it, like an ill-assorted flock of sheep, would come the wind." (My Family and Other Animals by Gerald Durrell)

Q: What does it stand for in this sentence?

Thanks.

The wind.
Driving the clouds before it[self], came the wind.
The wind came, driving the clouds before it[self].