Does calling Clear disposes the items also?

You should rely on Dispose() call when you're dealing with unmanaged memory, shared resources or large memory areas. Doesn't seems this case.

Q: Does?

A: No - Clear does not dispose the items (they could be used in other parts of your application).

So, if your ToolStripItems are standard .NET ones, should Clear be sufficient? After some reflection I'd say "probably not".

Yeah, this is true that if you will have any references to the ToolStripItem in other part of your application, the .NET GarbageCollector will destroy(use the class destructor) it automatically. But, it will not call the Dispose(true) method, that is, however, required for the form's IDisposable components.

Read a propos this and this.

Actually, I believe that you will, however, need to explicitly Dispose your Items, like the ToolStrip's Dispose method does (replace this by yourToolStrip):

if (!this.Items.IsReadOnly)
{
    for (int i = this.Items.Count - 1; i >= 0; i--)
    {
        this.Items[i].Dispose();
    }
    this.Items.Clear();
}

EDIT

I also created the following thread to clarify this question more generally.

Calling Clear doesn't dispose the items, but it removes the reference from the collection to the items. If that was the only reference to the items they will be garbage collected automatically at some point (which you can't predict, but you may control using the GC class).