US state region briefly features in song (7)
I believe the answer is:
arizona
'us state' is the definition.
(state of the USA)
'region briefly features in song' is the wordplay.
'region' becomes 'zone' (zone is a kind of region).
'briefly' means to remove the last letter.
'features in' is an insertion indicator.
'song' becomes 'aria' (aria is a kind of song).
'zone' with its last letter taken away is 'zon'.
'zon' going within 'aria' is 'ARIZONA'.
(Other definitions for arizona that I've seen before include "American state with Grand Canyon" , "Dry US state" , "US state containing the Grand Canyon" , "State of SW US" , "State in south-west US" .)