How to delete extra shape length field?

[MaryDuBose]

I have a feature class in a file geodatabase that was created through a join, and ended up with 2 shape length fields. The extra one was renamed Shape_Length_1 and all values are null; however, I'm not able to delete or modify it. Is there any way to get around this? I understand I can't delete the primary Shape_Length field, but I would like to have a way to get rid of the extra, blank, field. The Delete Field tool does not give me the option to delete this field at all.

[DanPatterson]

Is your join temporary?  

Add Join (Data Management)—ArcGIS Pro | Documentation

or permanent?

Join Field (Data Management)—ArcGIS Pro | Documentation

You should be able to delete the unwanted field using the latter.  Better still, specify the fields your want instead using Join Field

[MaryDuBose]

Hi Dan, I had previously joined data, and then exported to a new FC. I had created new feature classes using the Dissolve tool, to merge features with the same ID, and then joined the original data back to it on that ID field. When I did the join and then exported to a brand new FC, I didn't specify for it to join the old shape length field, but it did it anyway (as Shape_Length_1) and all were listed as Null.

[DanPatterson]

Long history for the data.  Have you tried

Feature Class To Feature Class (Conversion)—ArcGIS Pro | Documentation

you can delete fields, and/or change their properties.  Perhaps a combination of those will allow you to get rid of the field.