Is this employment?
If it is employment, I would call it employment/clinical.
If it is not employment, I would be hesitant to call it "volunteer/clinical" but I could stretch it that way if you are working through the volunteer office of the clinical facility.
If not, you could call it "research". Describe what you do. That is more important than any label. That you are face-to-face with patients who may become clinical research participants if they give their consent after talking with you, is a very valuable experience in my book. And of course you are responsible for them while they are with you. You need to assure their safety, their privacy, the confidentiality of their data.