(1) Of, pertaining to, relating to, or dealing with a (medical) clinic
(2) Relating to or founded on the actual observation and treatment of patient(s) (in contrast to theoretical)
The term clinical pertains to a medical practice, such as observing and treating patients. Examples of usage are the terms: clinical trial and clinical medicine. Clinical trial is a formal research protocol involving patients. Clinical medicine is the practice of medicine that is based on the direct observation of patients.