Result of the winter I'm afraid, not much you can do other than to feed it with something like Growmore, raked in round the roots,make sure it's not suffering from drought and keep it a bit sheltered during this current cold snap.

If there is any green left on the old fronds, cutting them all off will slow the recovery. As new fronds grow out of the center, cut off the worst of the old fronds, and the plant will gradually look better and better. As Bamboo says, a good feeding speeds recovery, too.