it’s very simple, because you must only define a “sort-column-id” for the column (GTK Version 3.24.5-1)
# define sort-column-id for a specific column
gtk_tree_view_column_set_sort_column_id(GTK_TREE_VIEW_COLUMN(firstcolumn), 0)
This function enables a “clickable column-header” and sorting (default: switches with every click between ascending/descending sortorder) for the row.