This is not a solution so much as it is a rewrite of the achievement's current HORRID description.
'Finish 1st in 10 ranked Backlot Races'
The wins don't need to be consecutive. You also have to make sure you're going for Backlot RACES, not Backlot BATTLES (which do not count).
Had to look up xboxachievements.com for clarification. The previous solution by CasperTC is fine; it was the lack of proper achievement description that confused me.