Its license plates say "Famous potatoes" (5)
I believe the answer is:
idaho
'its license plates say famous potatoes' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for idaho that I've seen before include "43rd US state" , "Rocky Mountain state" , "US state S. of Montana" , "The Gem State (US)" , "American state, capital Boise (5)" .)