It needs to be added to the description that you cannot attain this achievement until you have earned the Sore Fingers achievement and Addict achievement (For completing 100 full games and scoring 2,500,000 points cumulatively).
Once you have both these achievements, play a game, finish in the top 250 and it should pop.
Please note: I am aware I do not yet have this achievement so some would argue that I should not be posting a guide for this yet, but the achievement description is incorrect here, it is only correct on the actual Snap Attack app itself, which is why I have created the solution, to highlight the fact some people will be in the top 250 all the time yet this wont have popped and may not have realised the achievement description inaccuracies
If you are voting negatively, please state why and I will try and improve my guide.
Good luck, this one will take a while to achieve