There are several opportunities to get this trophy throughout the game, but the first is in Act 1. You need to wait until a Wakcha has caught sight of you, and then escape by jumping onto a platform that the Wakcha can't reach. In Act 1, you'll make your way to a windmill where you'll find the boat keeper tied to a post and a sleeping Wakcha above.
Climb the ladder up to the next platform and extinguish Teku's candle. Climb onto the next platform. Sneak towards the Wakcha and make sure to step on one of the grubs. This will wake him up. After he comes to his senses and notices you, quickly sprint off the ledge to the right. If you sprint too early before he's fully woken up, it won't count. He'll lose sight of you and you'll get the trophy.