Open grassland in the USA (7)
I believe the answer is:
prairie
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">open grassland in the usa</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for prairie that I've seen before include "Wide grassy plain" , "Cowboy song: ` `Bury me not on the lone .......' '" , "Large grassland region" , "Great grassland area" , "-- Dog; -- oyster" .)