If you are referring to the first cell in the InsertionRow, then you will need to handle its Loaded event, preserve a reference to it and then access its Cells collection to place the first cell in edit mode.

If you are referring to the first cell in the first datarow, then you will need to use the GetContainerFromItem method to retrieve the Xceed.Wpf.DataGrid.DataRow container and access its Cells collection (in the same manner as the InsertionRow). 

As for clearing the grid, I suggest that rather than clearing the data view that you set the ItemsSource property to null. You will also need to clear the grid's collection of columns if the next source you are binding too does not have the same fields/columns.

Besides clearing the entered data it also clears the insertionrow from the gridcontrol. Is there a way to not delete the insertionrow or redisplay it after the clear?

If the column definitions are still present, then the InsertionRow should remain; you may just need to set the Height property to see it.