Dreams about a pendulum are about your soul power, your source, your energy and your vibration, pay close attention to what the pendulum is made of (material) this gives you a good idea how to explain the dream or vision. The pendulum reflects your own energy and, as it were, the crystal and/or gemstone vibrational field.
Dreams or a vision of seeing a pendulum tell you about the search for inner truth, feelings, emotions and answers from the afterlife, answers to your questions, asking for help.
But also the spiritual cooperation between soul and spirit is at its highest level and you feel good and in balance with it, you can help other people with this power. An alternative explanation is that you are looking for a balance between the masculine and feminine, you want to solve doubts between yes and no in your life.
It reflects "Your gift, your inner strength, your heart, your source, the power of visualizing, manifesting and so on". It is a reference to becoming aware of that and activating your pure soul energy.
Another spiritual explanation is the connection with other extraterrestrial dimensions and of course the higher 5th, 4th, 6th dimensions here on Earth. In addition, it can refer to waking up and/or be a signal to the connection with spirituality and/or nature, religion, witch, wicca and so on.
In addition, it also refers to leis and crystal fields here on the planet - the connection to this and/or the signal that you can and/or may work with this.