Leyland Cyprus tree is becoming brown
Your Leyland cypress tree has a severe infestation of bagworms. Given the extent of the damage, it is unlikely that the tree will survive. It will certainly not regain its former viability.
The extent of damage suggests that this is the second year of bagworm activity in the tree. it is best to have the tree removed.
If you have other evergreen trees or shrubs in your landscape, it would be appropriate that you examine them now for any early signs of bagworm activity. If you see any of the bagworms crawling around the tree, you could spray them now with either Spinosad (Conserve) or Acitamiprid (TriStar).
Remove any bags that you can reach on your evergreen trees/shrubs during the winter and be prepared to spray next June.