The game put the leading teams up against one another and an explosive clash delivered on its potential, with seven tries and a red card for Tony Ensor.
Although Stade's Gael Fickou cancelled out George Moala's opening try, Clermont was in control throughout, crossing again through Morgan Parra and Wesley Fofana.
The game burst into life again with 10 minutes remaining as Ensor was dismissed and Clermont scored twice more with Moala getting his second and Judicael Cancoriet capping the home scoring.
There was still time for Etienne Falgoux's 79th-minute sin-binning to even up the sides, before Stade scored a late consolation through Julien Delbouis in the dying seconds.
Racing 92 fared much better as it thrashed Agen 59-7, despite a second yellow card for Joe Rokocoko.
Rokocoko scored the sixth home try of a scintillating opening 30 minutes and Racing continued to dominate throughout, with Louis Dupichot crossing for his second and the hosts' ninth after seeing his Rokocoko dismissed.
Meanwhile, Toulouse held off a second-half fightback from La Rochelle to triumph 33-26.
Elliot Roudil and Arthur Retiere each crossed twice after the break for the visitors, but five Toulouse tries, capped by Thomas Ramos, proved to be enough for victory.
Jonathan Wisniewski's five penalties carried Lyon to a 22-16 win over Perpignan, while Johan Goosen's late three-pointer from the tee got Montpellier a 9-9 draw against Bordeaux-Begles.