To clean a burnt fry pan you can use some baking soda and vinegar.
Sprinkle some baking soda into the burnt fry pan and then pour some plain undiluted vinegar into the pan and allow the vinegar and baking soda to react to each other.
Allow the baking soda and vinegar to sit in the fry pan for 10 minutes or so and then take a scrub brush and scrub the burnt fry pan and the burnt food or whatever is burnt in the fry pan should come out.
You may also need to heat the fry pan up to get really stubborn burnt food out of the burnt fry pan.
Another way to get a burnt fry pan clean is to sprinkle just baking soda into the pan and then add about 3 drops of dish washing detergent to the baking soda and then fill the fry pan to the top with some water.
Then put the fry pan on the stove and turn the heat on high.
Bring the water to a boil and then allow the water in the burnt fry pan to simmer for about 20 minutes.
This will or should help lift the burnt off food or burnt grease from the fry pan.