When you delete a part, all parts that have been created from that part are also deleted. This preserves and exposes the existing element.
To delete a part
- In the drawing area, select the part.
- Press Delete, or click Modify | Parts tab
Modify panel 
(Delete). A Revit warning displays stating "Edits to the model will cause some Parts to be deleted."
- Click Delete Element(s) in the warning dialog to remove all parts.