IS there fabric folded over encasing the whole elastic band, like it's in a long tube? Or can you actually see the elastic and it is stitched down to the suede?
If it's encased and seems loose inside the tube, yes, if you cut it, it will be like cutting a rubber band. However, you may be able to replace & insert a longer piece of elastic inside, then knot it to the right stretchiness for you.
If it is stitched down, then you can probably snip it in a couple places. The elastic sewn down has created permanent gathers in the fabric. If you snip it straight down, along the back of the boot, it releases one gather about 1/8" to 1/4". Try the boot on. That may be enough give for you. If not, over over about 2 inches and snip another gather at the back.
Third. If you don't want to snip the elastic, where the ends meet at the seam: take a seam ripper and gently take off a little of the stitching, where the elastic is sewn to the suede, maybe about a 1/2". If that seems like it would give enough slack, then cut the elastic at the seam where you ripped out the stitches from the suede. You'll end up with a little hangy tail of elastic unattached. If you have accidentally ripped out too many stitches, you can sew the elastic back a little. If you need more slack, rip out a little more stitches. When you have enough slack, just snip off the elastic tail. Hope those directions made sense.
