is it safe to give my newborn a second hand teddy from a charity shop?

I would wash it exactly the same as you would their clothes and make sure it dries really well

If it’s able to I’d stick it in the washing machine.

Yea ofc, just wash it well. If you can’t wash it in the machine, a thorough hand wash will be fine :)

Definitely safe, we have loads and she's never ill

Dettol disinfectant spray then hang it out on the line to dry