It has been a season to forget for Grenoble, who knew a defeat would consign them to the drop, but second-placed Clermont only led 17-6 at the break with Alexandre Lapandry and Fritz Lee touching down.
The floodgates opened after the break, though, and Damian Penaud scored twice, while Ludovic Radosavljevic, John Ulugia, Alivereti Raka, David Strettle and Setariki Tuicuvu were all on the scoresheet in the nine-try romp that ensures a play-off spot for the visitors.
Grenoble, meanwhile, can no longer accumulate enough points to reach 12th, meaning they join Bayonne in dropping down a division.
In a back-and-forth encounter it was the visitors who earned the victory, with Facundo Isa touching down twice in the closing stages.
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