This trophy is titled "Battering Ram" and requires you to ram a grabbed enemy into other enemies five (5) times.
On the very first level, while playing as the Custom Character, when you approach the police officers, there will be a Circle icon above their heads. Press the Circle Button to perform a grab. You can now run around while holding onto the police officer. All you need to do is charge into five other police officers to unlock the trophy.
I personally unlocked it on the second half of the bridge, which is essentially the second area of the level. Several police officers spawn. Just grab one and ram into all of them to unlock the trophy.