If you really want to apply a clear coat on your outdoor furniture, your options are limited since most exterior products need to be colored to offer protection against UV light. Otherwise, the wood will darken and become grayish over time.
One option however is Marine Varnishes from Epifanes, which are perfectly suited for this task.
A decent alternative in your case would be to use penetrating oils designed for exterior use, but in your case, you would have to select a color that closely matches the natural color of your wood. You might want to look into Broda Pro-Tek-Tor and Pareo /Pareo Zero products in this case. One benefit of oils is that restoration is much more simple than varnishes, as you don't have to sand everything off, just a light sanding + another coat of oil when the finish looks like it's slowly wearing off. Here's a short article on these products that we wrote a few years ago, should you be interested!
Should you have any additional questions or if you feel that the blog article did not answer your questions in a satisfying way, please do not hesitate to contact us again, and we'll be happy to assist you throughout the different steps of your project!