It could be a rudbeckia or echinacea....or it could be a weed.
For my part, I'd just watch it.

It looks to me like it might be a Solidego rugosa, rough-stemmed goldenrod. Toothed leaves (variable), fuzzy stem with reddish tint near the base, but I can't see how the leaves attach too well. Do the leaves feel fuzzy?

Here is a link that might be useful: leaves and stem for Rough stemmed goldenrod

Thanks both for your response.

I haven't any of these plants in my garden, but Rudbeckia, which I bought but I have deadheaded regularly.

babs I checked the leaf pattern and it doesn't match. I'll just keep an eye on it for now...