A visionary is someone who receives visions/apparitions as part of personal/private revelation. However, there are many false visions/apparitions and false visionaries, it is essential to carefully discern the spirit that is the source behind the visions/apparition. Is it the Holy Spirit, the human spirit or possibly even an evil spirit? Such people must submit themselves to the authority of Holy Mother Church, and be obedient to her even if what she, through her representatives (bishops and priests) contradict the messages of the visions. A true visionary will obey without question. If it is truly of God, nothing will stop it; an obedient visionary is a patient one, trusting that if the visions are of God, that God will remove any obstacles to the message. Disobedience to the Church is a clear sign of a false visionary.
A true visionary does not have visions that contradict Church teaching. I would not ask a visionary for advice without consulting one or more priests. If the visionary contradicts the priests and Church teaching, you must reject their advice. If the advice does not conflict with Church teaching, and a priest says it is okay to follow, than you may follow it if you wish, just as you might follow anyone’s advice that is compatible with Church teaching. You are safer to follow a priests advice, since if the priest is wrong, it is he who must answer for it. A visionary can lead one into apostasy, if the advice is incorrect. This is why the local ordinary (Bishop) of the diocese where a visionary resides, carefully examines and weighs the evidence regarding the authenticity of the visionary and any alleged apparitions. If the decision is neutral, we must proceed with caution; if negative, we must the visions altogether.