It depends on the specific job situation. In general, most academicians have some type of teaching responsibility. Teaching takes many forms. Some are required to give lectures to medical, nursing, allied health students as part of a class. Usually, clinicians oversee residents and students on their service and may give a seminar every now and then. For instance, being a surgeon on a service with residents and students is a type of teaching.
The type and amount of teaching you will do will depend on your clinical specialty and how much grant money you bring in. The more grant money you have, the more likely you will be able to negotiate a lighter teaching load.