There are several commands which give you control over the current window.
Choose Windows > Lower to push the current window to the bottom of the pile of windows on-screen.
Choose Windows > Raise to bring the current window to the front of your screen.
Choose Windows > Quit to quit any windows selected in the graph.
Choose Windows > Destroy to destroy any windows which are selected in the graph. You are prompted before the windows are destroyed.
LispWorks IDE User Guide (Macintosh version) - 25 Nov 2011