Empty CustomField

For some reason, on particular condition I have to remove values from custom field, however I cannot find any method to empty/delete these values or to simply set CF value to null.
I have found AddCustomFieldValue method - is there any other function that would allow me to set value, not to add another (or simply clean cf)?
Thanks in advance!

What happens if you AddCustomFieldValue as ""? Maybe this method too RT::CustomFieldValue - RT 5.0.2 Documentation - Best Practical