I think you may be on to something. Novak and Clarke have three decades of overlap in Washington going back to the Nixon administration. Clarke is just the type of source Novak would cultivate. Novak highlights Clarke's hard-line response to the Cole bombing in the column linked below.
Novak's column on "Losing bin Laden"
Is it possible that the whole Plame "Outing" was engineered to create a leak scandal for the Bush administration and create a retirement enhancing book deal for a friend, Ambassador Wilson?
It's also possible that in Novak's mind it was really no big deal...but he stepped on Wilson's parade, inadvertently fueling Wilson's self-promotion.