Darn.
Clones can be a pain but to expand on what @DonMorrison1 suggests, here is my method.
First of all, I suggest you upgrade to at least 2.7.4. As I mentioned I've experienced problems at 2.8 as well as 2.8+ so I'm using 2.7.4 myself
Cloning: Open ArcGIS Pro; down at the lower left corner you'll see the Settings 'gear' icon. (Don't bother opening a project per se, just Pro). Click on Settings and on the left panel, click Python. At this point you'll see your active environment. Notice below that I create a a specific target folder as well as naming convention for my clones:
I like to put my clones where I can find them rather than burying them where ArcGIS Pro does.
Assuming you have a target directory, let's set about cloning your Default Environment. Click on Manage Environments, and when presented with the Manage Environments pane, activate the the Default Environment with a single click. On the right side of the pane, is the Clone column; single click on the icon next to your default environment and you are presented with another pane that allows you to name your clone as well as put where you want it:
Click OK and let it do it's thing... Single click on the new clone and click OK to activate. Close ArcGIS Pro:
This is where my method is going to slightly change from @DonMorrison1 ...
Installing Spyder: Using your Windows Start button, navigate to the ArcGIS folder and select Python Command Prompt. It will be the new clone:
Personally I don't care for the ArcGIS Pro Package manager and prefer to use a Conda install for any custom installation of packages. Click here for a Conda Command Cheat Sheet.
I use this command for Spyder:
Again, let it do the mojo.... You'll get a Proceed ([y]/[n]) prompt: answer y. More bumping and grinding; be patient it may toss some warnings and other messages. Just let it go.
Once you return to the command line, type in spyder and see what what happens. I actually ended up with Spyder 5.0.4 because the 'channels' I go through didn't provide 5.0.5, but that's no big deal. You can always just update when you Spyder fires up.
That should just about do it....