In order to get this trophy you need to complete an 'Assassination Event' which is denoted by the Cross Hair icon on the map, in order to get your contract you will need to interact with the Pigeon Coop on the roof with
, the Coop will give you an area in the city of which you will need to search with Eagle Vision (Hold
) to find your target, they will be the Gold/Yellow highlighted AI. Once you have spotted your target you can either sneakily assassinate them or kill them however you see fit, so long as the target dies.
Note: Assassinations are unlocked a little bit after sequence 5 when you meet Lorenzo Il Magnifico.