A new low clock swing flip-flop (F/F) is proposed. The existing low clock-swing F/F's consume high power, introduce speed penalty due to contention currents or require large silicon area due to separate well for substrate biasing. By reducing contention currents, our proposal efficiently mitigates those issues. Measurements and simulations are carried out based on a 90 nm CMOS process, demonstrating reductions of active power by 71%, area by 36% and delay by 35% compared to previous proposals. It is shown that the combination of a lowclock swing distribution tree with the new F/F can save up to 60% of the total clock system power.