Rhus are renown for suckering. You need to dig out the remaining trunk, (assuming that you haven't already done this. The suckers will have become rooted so you need to dig them out individually. I might take some time but in the end you will succeed.

Thanks -sounds as logical I suppose-I will have to have a go as digging it out. Let’s hope the roots isn’t too deep.
Many thanks

you will laugh when you hear about my double whammy! I have Rhus and nearby a Sorbaria... They're in an area which is open and dry so I wasn't too worried about suckering... silly me! Only remedy I've considered is dig and pull the roots. hard work...serves me right for planting those two together! live and learn.

Thanks for answer- I’m afraid I did laugh because that’s the sort of thing I do. Come spring it’ll be interesting what the area will look like. As the previous answer I had says I need to dig out the roots. I wonder how deep they grow?

In the same family as some poisonous plants (poison sumac) it's advisable to wear gloves and long sleeves if working to eradicate them by "pulling"... roots of the initial plant are vertical but any offshoots run just under the soil can be removed and "pulled" back to the original plant. Otherwise, the sources of control info. that I've found, talk only about Garlon. If you're serious about removing it perhaps you would consider it, but my personal bias is that I want no chemicals in my garden at all; especially defoliants. I think I've got myself into a nasty battle...I'm going for control I still want the large original plant..it's just the little suckers I want to remove. I wish you good luck.