Thanks Hobo, The fan kills the battery life, and makes everything harder to listen to with YouTube, because the internal speakers on old MBP have next to nothing volume.
My only reasoning for blaming Sierra/Safari is only based on all the years of 10.6.8 that was trouble free, apart from Chrome eating CPU/fan with it's horrendous 'helper'. Just not had so many minutes in the day where the fan runs so often, since updating to Sierra. Seems over the top. And I like YouTube and watch it a lot, It's a glitchy nightmare in Safari. Open to full screen and it returns to small screen, every single time I click full screen. Comments and sidebar take an age to download, and click page back it does weird things and shows desktop and other pages before it does go back. It's really bad for watching YouTube so fan on for Chrome instead. Not just a few problems on YT, but many.
Just googled rtprotectiondaemon which is using 98% CPU every few minutes and aggravating fan, but it tells me it's related to Malwarebytes. I turned off their Real Time Protection, but it still would appear to be running, if that's on? Tempted to bin Malwarebytes now