Posted: 11/09/2014 at 21:46
Unfortunately, conifers don't sprout new growth from main trunks or branches. That section is dead as a dodo and won't recover, but you may be able to save the rest by cutting it out promptly, otherwise it might continue to die back to the roots (if it hasn't already.)
The conifers either side in the hedge will grow from the ends of their branches and will hopefully cover the gap in time. Nature abhors a vacuum!