A lawyer “on retainer” means a lawyer who is engaged by the client (they would retain the lawyer) to act in the best interests of that client without being limited by time or subject matter. Such a lawyer would not then be free to act against that client during the course of the retainer due to conflict of interest. The usual means by which a lawyer is placed “on retainer” is by the client signing a general retainer agreement and providing the lawyer with a sum of money (retainer fee) agreed by them to be kept in trust and applied to on-going fees and disbursements as incurred according to the retainer agreement for retainer services.