Hi, the leaves do look very similar to young Dahlia leaves, but at this stage it could be anything, your best course of action would be to allow it to develop further to get a more positive id, however a weed is a plant growing in the wrong place, which you don't want, so.if you don't want a Dahlia, presuming it is 1, in with your succulents, then that qualifies whatever it is as a weed, Derek.

You have a very attractive succulent trough so, whatever the plant and it does look like a dahlia, I would just pull it out now. It is not worth spoiling your display.

It looks like an elder seedling.