Hee hee. But no, I didn't mean a "potion of cleverness", I simply mean "be clever and invent a potion. Then use that potion as an ingredient to place the quality of the mental work of inventing a potion into a potion... then use that potion as an ingredient, etc.."

And actually, we know Harry meant to investigate mental magic, but we're not sure if he ever got around to it. (And, of course, there is Rowena's Diadem, which would seem to be an intelligence augmentation device. If that's in MoR, Harry's got to do something with it at some point. (But then, harry hasn't yet really jumped onto the existence of the Philosopher's Stone, so... well, I guess everyone here's already waiting for when he notices that and Epic Rages at the wizarding world along the lines of "you mean you already know how... you... ARGH!")

And we'd expect Ravenclaw members to already be using any clever potions or at least have rules against them (either imposed by the school or by themselves as 'cheating'). In canon, they all know about the Ravenclaw diadem which is supposed to make you more clever. So it's reasonable if there were any such thing, Harry would have been told about it (everyone knowing his interest in self-improvement or being more clever), heard of it, or read about it by now.