What do you want to go to the clipboard? Something that can be cut and pasted outside your application? In that case you have to convert the structure to a
string and export it to the clipboard.
Alternatively, if you want to copy a node object to another section in a tree, you essentially simulate your own clipboard. When someone copies/cuts, mark which node is selected, then when they paste perform a node copy.
Keep in mind that the notion of a clipboard is an abstraction, there's no hidden clipboard in your system.