removing squares from outside of circle

Dreama,

You might like this way, starting with the circle and the gride of squares (some of which look a bit funny):

1) Select the circle and Ctrl/Cmd+X+F+C+F (hold Ctrl/Cmd and press X then F then C then F, to make sure the circle is on top of the squares and make a copy of it in front of itself;

2) Lock the copy circle in the expanded Layers panel, it will be the topmost object;

3) Select the original circle and all the squares, the Pathfinder>Divide and delete all the bits of squares outside the circle (deselect and then ClickDrag over each (set) of the bits without including the circle and press delete twice each time to also get rid of stray end points).

Now you can add the legs and boots (will it become a bootlegger?), either working with the Group from 3) and leaving the copy circle from 2) out, or you can lock the Group and unlock the full circle from 2) and then work with that.

In the former case, you can skip the copy circle altogether.

Always backup your artwork before changing i irreversibly beyond Undos.

Can you show your layer structure? Probably, easier to find them in layers and delete.

Does a clipping mask work in your situation? It will not "really" cut it off, just hide it.

https://helpx.adobe.com/illustrator/using/clipping-masks.html