Menu subwindow doesnt disappear after I select it.

I created some menu via GLUT. When I am selecting some item of it my program clears the window by glClear(GL_COLOR_BUFFER_BIT) and draws some object but the Glut Menu Subwindow is still present on the window; only after next operation it disappears.
I couldn’t find how to manage this subwindow disappears immediately I select some menu item.

Thank you in advance