This sounds to me like a classic case of a negative entity spiritual attachment to an object. But this could very well be a demonic or other vengeful restless spirit or ghost.
In dealing with negative entities, it is most important to understand that they are simply spirits of humans with bad dispositions and possibly ill-intentions. They are not demons, devils and the like. The source of any negative entity's power is through invoking fear into their victims. If successful, fear will allow a negative entity to gain control over the mind of the person whom they seek to attack or influence. Unfortunately, most people fear what they do not understand, so it is easy for a negative ghost to find fearful victims.
If you don't want to rid of the grandfather clock, then these are some ways to rid of the negative entity:
Fuming is a process of burning dried herbs to banish unwanted entities. Clouds of fragrant smoke ward them the same way bug repellant can ward mosquitos.
To fume, place a heat-proof pot on a heat-proof surface. Light an incense charcoal briquette (never use barbecue charcoal, which is toxic when burned indoors) and put it in the pot. Then open all the windows and sprinkle a spoonful of herbs on it every few minutes to build up billows of smoke.
Certain herbs repel entities and make them slink back from where they came. Use sage or thyme if it?s a minor problem. If you feel the entity is mischievous or maligning and might not want to leave, use something stronger such as garlic powder, juniper berries, cinnamon or cloves. Leave the room if using these stronger herbs and come back when the smoke clears.
As you begin sprinkling the herbs on the hot coal, tell the entities very clearly that you want them to leave.
Water if Oil
Blessed water or oils banish entities, particularly those with more evil intent. Many churches sell holy water, but you can have your clergy bless it or bless it yourself with a prayer. You can also say prayers to bless a vial of olive oil, clove oil or cooking oil mixed with chopped, raw garlic.
Sprinkle holy water, or dip your finger in oil to draw a religious symbol (such as the cross) or a protective symbol (such as the 5-pointed star) on every door, wall and window in the house.
As you go from room to room, utter blessings and prayers from your Higher Power to assist you, and firmly tell the entities they?re not wanted and must leave.
Salt has long been used as a protection from unwanted spirits and entities. Bless a bowl of salt and throw handfuls around the room, charging the entities to be gone. Protect your home further, place a line of salt across every door that leads into your house and across every windowsill to create a barrier that will repel spirits.
Some spirits and entities are stronger than others, or their intentions are so evil that they are not easily deterred. If you have a very nasty intruder, things may not improve?or may get even worse! While these cases are rare, it is the time to call in a professional medium, spiritualist or clergy person to help you. I would get a preist to come and bless the object and your house.