US “Bluegrass” state (8)
I believe the answer is:
kentucky
'us bluegrass state' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for kentucky that I've seen before include "American state" , "Bluegrass State, famous for breeding horses" , "US state, capital Frankfort" , "US state with an annual Derby race since 1875" , "In USA it is know as the Bluegrass State" .)