Creating a mask to simplify map

[CourtneyThompson2]

Hi, I need to make maps of 20 separate sub-basins.  I would like to mask the sub basins not in use so that it shows up white all around the sub basin to be the focus.  I tried just making all of the ones not in focus white and the one I want hollow so that the data shows, but then the labels of the reference data (township and sections for example) still show over the top of the white polygons and it doesn't look very good...any ideas??

Thanks so much!!

[AbdullahAnter]

If you have a polygon for each sub basin, you can use it as the following picture:

Open Data Frame Properties > Data frame Tab >in Clip options choose Clip to shape > click on specify shape > in the new window choose outline of  features > finally choose your sub basin polygon that will be used to mask.