The sprout is most likely some type of lemon or lime, as Kaffir are not compatible with a lot of others. It appears big enough now to cut and root.

Thank you. Will cut later today. Any tip for successful rooting?

Air-layering is the safest way to root that branch. It should have hardened wood in center in order to strip down a inch of bark from it, and from your picture is to early for this.

I would not want it to leave on the stem for too long as it seems to grow very vigorous. I guess I will just have to take my chances.