Crude oil in USA — and a state (9)
I believe the answer is:
louisiana
'state' is the definition.
(I know that Louisiana is American state)
'crude oil in usa and a' is the wordplay.
'crude' indicates anagramming the letters.
'and' says to put letters next to each other.
'oil'+'in'+'usa'='oilinusa'
'oilinusa' with letters rearranged gives 'louisian'.
'louisian'+'a'='LOUISIANA'
(Other definitions for louisiana that I've seen before include "American state, capital Baton Rouge" , "Southern United State on the Gulf of Mexico" , "IOU a snail over in the US state" , "that's near Mississippi" , "US state, capital Baton Rouge" .)