Delete a Custom Field in your account if it is no longer needed. When deleted, the Custom Field is removed from any person on your list with the Custom Field set.
Once the Custom Field is deleted, there is no way to reverse the process and reset it for the people on your list.
To delete a Custom Field:
Click Custom Fields
Locate the Custom Field you'd like to delete
To the right side of the Edit button, click the drop-down
Click I’m sure, delete this field