How to dump a postgreSQL/postgis sample database filtered by a spatial extent?
Might not be the most elegant solution, but you can use the pg_dump utility to copy the DB and then overwrite the data in the spatial tables of the new, subset DB using the ogr2ogr utility. Run pg_restore and then ogr2ogr with your clipping method of choice. To overwrite the spatial data so that it is constrained to the extent of a shapefile, for example, run something like:

ogr2ogr -overwrite -update -clipsrc clip_shape.shp PG:"host=subsethost user=subsetloginname dbname=subsetdb password=subsetpassword" PG:"host=originalhost user=originalloginname dbname=originaldb password=originalpassword"


Check pg_dump and ogr2ogr documentation (linked) for details on the optional switches. Combining the two utilities should get you squared away.