By 'Tea Olive' I'm assuming you mean Osmanthus fragrans. Likely its gone short of water at some point, meaning its upper leaves dried and went brown - the fact its now showing green growth at the top probably means that its water shortage was a temporary state. It might mean your irrigation is insufficient in that part of your yard if the weather is very hot and sunny. That's all I can say without seeing pics of the plant itself, and assuming you've inspected it thoroughly for signs of infestation or disease. Give it extra water, cut down to the lower, green growth to encourage new growth - UNLESS you live in a cold USDA zone and winter sets in early, in which case, you'll have to wait till next spring to cut it down. Bear in mind that any shrub or tree needs copious amounts of water during its first two years - after that, they cope pretty well when water goes short for a while.