Learner's definition of CLINICAL
1 always used before a noun : relating to or based on work done with real patients : of or relating to the medical treatment that is given to patients in hospitals, clinics, etc.
Both experimental and clinical evidence show that the treatment is effective.
She enjoys her clinical practice but is looking forward to working in a laboratory.
Three hundred patients were involved in the clinical study.
a drug that is undergoing clinical trials [=scientific tests to see the effect of a drug by using it with real patients]
He's a clinical psychologist [=a psychologist who works with patients] and professor of psychology at the university.
2 : requiring treatment as a medical problem 3 always used before a noun : of or relating to a place where medical treatment is given : of or relating to a clinic 4 [more clinical; most clinical] : not showing emotion or excitement 5 : very exact or skillful