I am not sure what type of plant you are asking about. In general if a plant has brown stems and leaves and you cut back to the point where you see green wood the plant will regenerate. If the brown leaves and stem is due to a disease or other pest it may just continue to turn brown, then die. Cold damage or winter injury can sometimes cause new growth to die off so pruning back to green growth will be good for the plant. Lack of water can also cause brown leaves and so can root damage from a transplant or burrowing animal. Cutting back the damaged growth can stimulate new growth if you keep the plant watered while it regrows a root system. If you send more details about what type of plant and when you noticed the damage and a photo I can be of more help with this mystery of the browning plant. Just know it is okay to cut off the brown leaves and stems. Keep growing, Marianne Binetti