Chapter 11: Hidden in Plain Sight
As the trophy description says you must climb to the top of the clocktower. This can be done when you have to ring the bell near the top of the tower, but the handle breaks. Before you jump on the bell you must climb the wall outside the building. On the area above the bell is a treasure and some wooden beams. Go across the beam in the middle and you'll be abe to climb the back of the wall all the way to the top. Now just stand on the pillar on the rooftop and the trophy unlocks.