I am assuming it is a Tree Fern, ??? if so are you refering to the dead fronds that have frost damage ??? if you are, then that is quite normal as they are desiduos, it would be nice to see a picture to try and identify the species as some are more tender than others. :)
If it is frost damage then there is little you can do to save it, although you may be lucky and get growth from the base of the tree, only time will tell. :-\
Give it copious amounts of water and keep your fingers crossed. ;)
