How do i clean a brush used for lacquer?

You need to use paint thinner on it. Get a jar with thinner in it and when you are done with the brush hang it into the thinner. Like hanging the brush from a string, and letting the bristles submerge in the thinner a little while. You shouldn't get the handel wet with the thinner. After about an hour, take it out and start wiping the remaining varnish off of the bristles using an old rag you can throw away. Clean it real good, down to the nub or butt of the bristles. When finished, You don't need to throw away the thinner. Just let it settle and strain it into another jar for later use. You'll be happy you spent the money and got a good brush and you will be able to tell the difference after you have used it a couple of times.