I would use tite bind glue and create something to push the piece tight until it dries.

The piece was originally glued so as suggested above you can re-glue it but that takes same time and skill as replacement. To do it right both pieces must be pried out so mating surfaces can be cleaned before applying glue then properly clamped until bonded.

I would be concerned about the stability of a glued step. Have you looked into replacing the tread?

Take a picture …back far enough… to see the whole step and the riser supporting it…and also how deep is the overhang?..one possibility would be to bring the riser forward ..by adding another one over the existing one…to support the riser better…

Possibly allowing the cracked strip to look like a trim?

" I would be concerned about the stability of a glued step. "

Most every tread sold today is several pieces of wood glued together in width, solid 1 pc treads are limited to yellow pine for the most part. Klem is correct, has to come out to be glued properly after prep.

To repair you'd pull out the tread, joint the surface to get a good gluing surface (clean, flat, and perfectly mating), re-glue the boards together, (Titebond II is a good choice) and then re-install. Almost impossible to do in place because of the difficulty of getting flat, clean mating surfaces to glue. Squirting glue in the crack and hoping won't work, adhesion between the old and new glue is inadequate.

If you wanted to go that route, assuming the nose piece has come free, you could use a slot router bit to create a dado in the fixed part of the tread, a matching one in the broken off nose, and then insert a shim into the groove. The groove should be about half the thickness of the steo and at least a half inch deep on each side. This will give you enough good gluing surface to keep things together. Use a matching, strong wood (oak) to make the shim. You'll have to figure out a way to clamp the joint.

It will be easier, with a better outcome to remove the tread and fix it properly, or replace it with a new board. If the split is uneven such that jointing it will remove any significant width you'll either need to replace it or add a filler strip to maintain consistent tread width.

As a makeshift repair you could screw it in place. Drill oversize holes in the loose piece, then appropriate size pilot holes in the remaining tread. Use a hefty wood screw (#12) that is long enough to go all the way through the broken off piece and at least 1-1/2" into the fixed tread. This is not a plce for drywall screws! Countersink the heads so they don't stick out. That's a highly stressed location so I really don't recommend this. I'd use 5-6 screws across the width.

That looks like a oak nosing

Take it out, use good quality glue, and use #8 2 1/2" construction trim-head screws, fill the screw holes with stain-matching filler and you should be good to go.

Thanks all! Here is a pic of the whole piece. Not even sure how I would begin to take off the tread and subsequent bannister pole…..it’s a 10.5 inch tread w 1 inch overhang.

I tried to get a carpenter to quote and he looked at it then never got back to me…….so trying to figure out how to do it myself but I’m not very handy at all.

Here’s the pic