It's the fruiting body a bracket fungus of some kind and it shows that the branch is already decaying on the inside. There's nothing to be done about it. I'd suggest cutting off the branch. Cut back into healthy wood, if there is any.

Agree with the above. Once that sort of fungal organism appears, the tree (or branch if not on the trunk) is dying from the inside out. But trees showing these sorts of growths can often live on for many years, with the exterior portion of the wood providing the support and the transport pathways for water and nutrients.

thanks so much for suggestion , i will cut back the branch in spring .