Sorry, I don't know either. I'll guess that it's something like a 'hay-seed'.(?)
I got the impression 'clover' referred to the pro-government control freaks that were taking over the rural areas...
An excerpt: The true Clover, you see, is not merely a bad driver. He is a bad driver on a tear; angry at the world and in particular, anyone who doesnt view the world in/through Clover-colored glasses. That would be anyone who doesnt automatically worship The Law (any law; every law) or who isnt consumed by a desire to make sure everyone else obeys The Law.
Basically, the Clover mentality is that of the sheep, slavishly conforming to society, and scorning those who don't.