Chicago area
I believe the answer is:
loop
'chicago area' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loop that I've seen before include "Noose" , "Oval-shaped coil" , "not informed one's out of it" , "Curve that bends round and crosses itself" , "Aircraft manoeuvre; encircle" .)