The description should be "beat the high score on a contract"
Update : It sounds like my explanation was a bit weird/not complete, please find some clarification below (It sounds that you have to play it 3 times instead of 2) :
It could be done on your own contract by beating your best score. So the trick is :
1st playtrough : You need to create the Contract,
2nd playtrough : Play it slowly to score a low score
3rd playtrough : play it faster to get a better score and pop up the achievement.
I have done it on the first map with the jet fighter :
To create the contract :1 - Start the contract creation,
2 - Mark up the 1st guard as target
3 - Wait 20 secs
4 - Kill the guard with gun
5 - Escape using the button.
Replay the contract and set a low score :1 - Start the contract
2 - Kill the guard with gun as soon as you spawn
3 - Wait 10 secs
4 - Escape using the button.
If you do not pop the achievement you havee to replay a 3rd time as below :
Replay the contract and set a high score :1 - Start the contract
2 - Kill the guard with gun as soon as you spawn
3 - Escape using the button.
As you should be faster, you get higher time bonus therefore you beat your highest/previous score and pop the achievement.
Remark from
Megamonkeymania : Replay it as soon as you do your first run to avoid other player to score the high score