How to Delete An Attachment

An author asked "Do you know how to undo an attachment? I attached something and later found something better, but I can not figure how to undo the original attachment."

Here's one way to fix this problem:
Make a new card.
Copy the contents of the old card.
Paste the contents of the old card into the new card.
Delete the old card with its attachment.

Is there a better way to remove an attachment?