Clermont came from behind to clinch a 19-18 victory over Toulon thanks to Damien Chouly's late try at the Stade Vélodrome in Marseille.
Les Jaunards as a result extend their advantage in first place of the Top 14 to six points ahead of Montpellier.
Toulon lost France captain Guilhem Guirado after half an hour to injury in a contest dominated by penalties from both scrum-halves.
Jonathan Pélissié struck twice in the opening 11 minutes and issues at the breakdown for Clermont allowed him to make it 9-0 before the end of the first quarter, as Toulon took control.
Josua Tuisova's struggles under the high ball allowed Morgan Parra to kick Clermont's first points with a 26th-minute penalty, following that up with another three points after Toulon infringed at the scrum to close the gap to three.
Pélissié tried to respond, but his effort from 40 metres out struck the post, leaving the score at 9-6 by half-time.
Parra's next effort suffered the same fate, rattling the post from much closer, as Pélissié responded with two penalties in four minutes to make it 15-6.
Toulon being immediately penalised at the breakdown enabled Parra to respond, knocking over three points, and he stepped up again when Jean Charles Orioli was penalised on the edge of his 22 to close the gap to just three.
A miss and success off the tee followed for Pélissié, as Parra failed to land his own fifth penalty leaving Clermont trailing by six in the closing stages as the contest looked set to finish without a try.
But Clermont had other ideas – a moment of genius from Scott Spedding unlocking the defence as his low grubber kick freed up Alivereti Raka to cut inside to feed Chouly for the try under the posts, Parra converting to give Clermont the lead at 19-18 and ultimately the win.
Pens: Pélissié 6
Pens: Parra 4
Toulon: 15 Drew Mitchell, 14 Josua Tuisova, 13 Mathieu Bastareaud, 12 Ma'a Nonu, 11 Bryan Habana, 10 Tom Taylor, 9 Jonathan Pélissié, 8 Duane Vermeulen, 7 Steffon Armitage, 6 Juan Smith, 5 Romain Taofifenua, 4 Mamuka Gorgodze, 3 Levan Chilachava, 2 Guilhem Guirado, 1 Alexandre Menini
Replacements: 16 Jean Charles Orioli, 17 Xavier Chiocci, 18 Thibault Lassalle, 19 Juan Martín Fernández Lobbe, 20 James O'Connor, 21 Frédéric Michalak, 22 Éric Escande, 23 Manusa Saulo
Clermont: 15 Scott Spedding, 14 Alivereti Raka, 13 Jonathan Davies, 12 Isaia Toeava, 11 Noa Nakaitaci, 10 Patricio Fernández, 9 Morgan Parra, 8 Fritz Lee, 7 Peceli Yato, 6 Damien Chouly, 5 Sébastien Vahaamahina, 4 Flip van der Merwe, 3 Dan Kotze, 2 John Ulugia, 1 Raphaël Chaume
Replacements: 16 Benjamin Kayser, 17 Thomas Domingo, 18 Arthur Iturria, 19 Judicael Cancoriet, 20 Ludovic Radosavljevic, 21 Brock James, 22 Aurélien Rougerie, 23 Clément Ric
Referee: Mathieu Raynal