US river (8)
(Other definitions for potomac that I've seen before include "Water flowing" , "Washington's river" , "River of Washington DC" , "Capital outflow" , "to which banks in Washington have access" .)
(Other definitions for missouri that I've seen before include "River joining the Mississippi south of St Louis" , "US state, capital Jefferson City" , "American state, capital Jefferson City" , "So is rum I alter to the state" , "State of central USA" .)
(Other definitions for colorado that I've seen before include "Beetle whose larvae destroy potato plants" , "US state, W. of Kansas" , "US state in the Rocky Mountains" , "US state (with a beetle)" , "US state has a strangely cool road" .)