that is the MAF screen. it directs the air to flow straight over the MAF sensor for a better reading. to remove it, use a snap ring pliers or something similar to remove the snap ring that holds it in.
once you have the ring out, use a bend paper clip and insert one end into the MAF screen to try to pull it out. BE CAREFUL, it bends VERY easy.
HOWEVER, you will probably have to remove the throttle body entirely to clean it. Most of the dirt is on the inner part. Your throttle body will probably look very clean on the other side.