Some clergy are well-trained in counseling addicted people, and some are not. If your clergy person has training and experience in helping teenagers with drug or alcohol issues, he or she should would be a great place to start! The advantages that clergy have is that they 1)share a set of faith-beliefs with the members of their Church/Synagogue/Mosque, and 2 have an initial trust relationship with those who come in to see them. (Therapists can't be expected to have either!)
So,if you are worried about your own behavior with drugs/alcohol, or the behavior of a loved one, your clergy person would be an ideal first consultation. If you need formal treatment, your clergy person will likely be able to find a treatment facility which has a philosophy consistent with your own beliefs and worldview.Of course, some clergy have received advanced training in counseling or psychology, and might be perfectly capable of treating an addicted person. As always, when you are looking for a clinician, you should ask about the person's experience and training in treating addiction, and make sure that you are comfortable with his or her treatment philosophy and demeanor.