### Clue: First couple in Arizona initially leaving another part of US for a third (6)
### Answer: KANSAS 
 ### Explanation: Definition: a third
A subtraction: [ar]KANSAS ('another part of US') minus AR ('first couple in **AR**izona'); 'initially' simply says that the removed letters are at the start; and, of course, the 'third' is yet another part of the US.