If the data in that particular section is characterized by a specific attribute, you can use a definition query to filter out the unneeded sections. Right click your layer in the layer list and choose properties then select Source and click on Query Builder:
In the query builder, select the field that contains the attribute and fill in the query that corresponds to your data. In the example here, only the points that have the munic_id equal to M1005 will be displayed.
If no such attribute exists, you can select the data located in that section and copy it to new layers. Another way is to assign an attribute to the data belonging to that section and apply the query filter afterwards.