Possible Clues:

• Tons left in country's oil centre
• Oklahoma university city
• City whose name means 'old town' in Creek
• Southern oil center
• 'Livin' on ___ time' (lyric in a #1 Don Williams country hit)
• A floozie from the right part of Oklahoma
• Top of apple tart turned up in US city
• Oklahoma county or its seat
• Where in the States a trollop's brought up
• A drab over in Oklahoma