A lawyer is a person who represents the interests of a person, for example, in a court of law. The role still existed in the 24th century.
"Conservator" is the Cardassian equivalent of a lawyer. (DS9: "Tribunal")
After Kay Eaton disagreed with her husband Julius' idea on what to do with Benny Russell's Deep Space Nine story, Herbert Rossoff told her: "You tell him, Kay. I know a good divorce lawyer if you need one". (DS9: "Far Beyond the Stars")
After he was arrested by Odo for smuggling kemacite, Quark told Rom to get him a lawyer. Rom suggested that he would contact Gaila for one. (DS9: "Little Green Men")