There are clean installations of Windows and then there are OEM "clean" installations of Windows. An oft-recommended tip for anyone upgrading one version of Windows to another (even a new Windows 10 build) is to use the "Reset" feature in the OS to reinstall the entire OS. The problem, though, is that if the computer vendor preloaded Windows with software, or "bloatware", then that reset feature isn't going to help.
That doesn't mean, however, that you're out-of-luck with reinstalling a truly fresh Windows 10. Microsoft has publicly released a tool (after being introduced to Insiders over the summer) that will help you get the job done. After downloading the tool at the URL below, Windows will reinstall itself to match what you'd get if you were to install from the most recent DVD - sans bloatware.
There are a couple of things to bear in mind here. First and foremost, you don't have to lose your files by doing this; you'll be provided the option to keep them. Second, you may run into some roadblocks with regards to app licenses (eg: the preinstalled apps that are no longer preinstalled). That even includes vendor-specific drivers, so if your notebook or desktop has special hardware that Windows 10 can't install on its own, you'll need to hit up the vendor's website to download and install the drivers manually.
Microsoft also notes that if an Office 365 subscription was included with the PC, that it can still be taken advantage of, but the software will need to be downloaded manually from the official Office website (which is actually very simple).
So there you have it. If you've been craving a truly clean Windows 10 installation, your solution has arrived. We think Microsoft deserves a kudos for this; this is a tool it didn't have to release, but it's extremely useful for those who like their OSes being kept as clean as possible.