Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
You mean the vent? It's located in the hinge itself, so you can't really clean it.
 
when you close the lid, if you look at the hinge from the bottom side. you can see vent lines inside the hinge. You can blow it with compress air to remove some dust :eek:
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.