Definitely the shoot below the graft line has been growing for a number of years now. Look closely at the union to the main stock and hopefully you can make a clean cut and remove it.
However, it may be too late if the union has weakened the actual grafted portion union. If you had a close up of the lower base of the plant to view I could give a response on which I would remove.
No guarantees at this point as I would consider this one " major surgery"
