A TOTAL LOSS: Lexington Fire Department crews are responding to a fully involved barn fire Tuesday afternoon in the 5000 Paris Pike.   Officials reported that firefighters were dispatched at around 3:15 p.m. to the scene, where a large barn was fully engulfed. Windy conditions are driving the fire, LFD added.   Due to the extent of the fire, crews are operating in a defensive mode. The barn is reportedly a total loss.   Extra units were dispatched to help with water supply. Firefighters are focused on protecting nearby exposures, LFD reported.