What does it mean?
The circular dependency error tells you that you are creating a circular dependency by using the same field names for two different fields in the import mapping of your project. The image below shows an example of this.
How can I fix it?
In this case you should rename one of your fields in your import mapping. Following the example above, it would make sense to rename the "content" to "content" and the "description" to "description". However, you can type in any field name that does not exist yet.
You can edit the import mapping via "Setup" in the left menu, and then clicking "Edit mapping". After changing the field name, do not forget to click "Save & import" at the bottom of the page.