Leicester Tigers centre Guy Porter was sent off for an ugly head collision with Clermont No 8 Fritz Lee with the referee's decision to brandish a red card dividing the room.
The visitors came away with a historic win nevertheless with Ellis Genge among the try-scorers as Steve Borthwick's men left France with a 29-10 advantage.
The teams meet again at Welford Road next Saturday with aggregate scores over the two matches deciding which progresses.
