Sick Vine Maple?
That looks very much like drought damage. I would leave it alone for now and see whether it leafs out normally next year. It probably won't, in which case you can remove the dead branch at that time. But there's no harm in waiting. You can also tell whether the branch has died by scraping away the outer bark with your fingernail. If the inner bark is still green, the branch is still alive; if brown, it is dead.
If/when you remove the dead portion, make your pruning cut in the live portion of the branch, just below the dead portion. That will help the tree seal over the wound more quickly.
Thank you. I did the fingernail test and it was green. I will increase the watering and see if it leafs out next spring.