spray clear coat left white spots how to fix on wood?

You should repaint the whole area. It's not going to be easy to get those spots off without sanding the whole thing first. You can try sanding it with 220 grit sand paper and then washing it with water, but it's hard to say how well that'll work.
This is a great question and one that I get asked all the time. The best way to fix this issue is to sand the affected area, and then re-spray with the clear coat.