I am using ArcGIS-10.3.1. I have a feature layer that includes total population by census tract (and includes lots of other info like shape length, shape area, population density, etc.). I have an 11-km square polygon drawn on the map (just using the ArcMap drawing tool). I want to know the total population that resides within the 11-km square. The square includes some whole census tracts within it, but cuts across some others.
I assumed I could use the Clip tool somehow, but I'm unsure if it's even possible to clip a feature layer based on a polygon. And, I'm unsure how to turn the polygon into a feature layer to then use it with the Clip tool.
Any ideas on how I could do this? I'm a complete beginner - I can make maps, but don't know how to use Tools well.