A spoiler for a widget?

Please explain more what you want to do.

If you mean hiding some text until something is clicked to reveal it… try this: https://www.farinspace.com/wordpress-peekaboo-plugin/

I’m using it on a site right now with good results.

No, I want to hide/show a whole widget on the sidebar.
So if someone would click on it, the widget would be shown or hidden.

Maybe the Tabbed Widgets plugin will do what you want.

Ah thanks. That helped ??