This is the card of Wisdom, of applied knowledge and can also indicate schooling and learning .It represents guidance from within, the realisation of inner aspirations by an occult isolation .

Because he is a werewolf, Remus always had to hide, I suppose that he had always been alone, since the Potters' death.-that's for the card's isolation aspect.

About wisdom and knowledge, he was a real guide for Harry in book 3, and actually he is the best DADA professor in Hogwarts.