Inspired by the use of springs in 3D Printy's model https://www.printables.com/model/155771-wall-mounted-cat-toy but not wanting to spent too much time attaching it to a wall, I spent hours making a clamped version.

Our cats love the stick toys with feathers at the end, so I included a way to attach those. It's optional, it also has a hole at the end of the sping to attach other toys. This part uses 2 m3x10 bolts with square insert nuts. These are commonly used in prusa printers, so I figured these would be available to a lot of people here. 

Printing

Print everything in the orientation of the file. No supports

Print the spring with enough perimeters to print it solid. I'd also recommend printing the clamp pretty strong or will probably warp when clamped for some time (atleast 3 perimeters and a bit of infill). 

I used PCTG for the spring, PLA for the other parts. I like the PCTG for it's flexiblity, it's comparable to PETG. PLA might be a bit stiff, let me know!