The question is presented in broad terms. Before you answer it, you should narrow the focus of your paper. If you are writing about a legal clinic, for example, you may limit your paper to lying on behalf of clients. If you are writing about a health clinic, you may focus on lying to patients. Once you have identified the limits of your topic, be sure to express clearly how you are defining a lie.
Many definitions are possible.
First, you should describe a number of situations or problems. These may be actual or hypothetical. The situations should cover the range of problems your analysis is addressing. Second, you should analyze the competing pressures, recalling that a professional may have duties to her or himself, to a client, to an employer, to third parties, to the public, to her or his profession, and perhaps to others. In is useful to think of competing pressures in terms of these duties.