NO CARMAKER I know covers the clutch under warranty. It's regarded as a consumable item, so I'm not surprised Nissan has refused. But at only 40,000km I would have thought it would have come to the party with at least part of the cost of replacement. It would be a tough battle, but if you feel aggrieved, pursue it further with Nissan. You could go to VCAT and get a ruling, but again, it's unlikely to be worth your while.