When Lily calls you to rescue the survivors, head to the marker for Besieged to help out some survivors in a nearby house. After killing the initial zombies, talk to Eleanor to help defend the perimeter. Don't take items from their supply locker to not lose their trust. Help them barricade the windows around the houses first. Then head outside yourself to kill zombies smashing the barricaded windows. When attacking a zombie near a window, don't do the dropkick as the input for A will make you jump into the window and get it destroyed.