Try vacuuming it if not it should come off do this when cool
You should be able to remove it by undoing clips or snapping it out. Sometimes you have to push up on one side first to release the entire screen downwards. Take outside, spray it with cleaner, scrub, then rinse well with garden hose.
Soak it in some Dawn dish liquid and hot water. Rinse and dry. I stick mine in the dishwasher.
Yes, good point from William that some screens are small enough to put into the dishwasher. The strong soap with high temperature water is a sure combo for de-greasing.
Most of them come off and can be put in dishwasher cycle. They are made of aluminum and wash beautiful.
I soak my screen in degreaser ( Mean Green) . Don't know if it is only sold in Canada.
I have sprayed mine real good with oven cleaner in a foil pan and let it soak overnight then rinsed it and do it again until you are satisfied, It worked for me.
Remove, wash with dish detergent in very hot water. The hot water melts the grease. Some people even boil them in a pot (if they are all metal).
Put it in the dishwasher.