The phrase "the only means" is correct and usable in written English. You use it when the thing you are talking about is the only method or way to do something. For example, "The only means of getting to school on time was to take the bus.".
That's the only means of winning".
For her, fighting is the only means of discovery.
But test scores could not be the only means".
The only means we have is public pressure," Patel said.
But TRPA1 is not the only means of infrared sensing.
War was the only means of resolving the issue.
One of the only means of resistance is public protest.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.