FBI Director William H. Webster said yesterday that his agency is cracking down hard on organized crime with increasing signs of success.

So far this year, Webster said, the government has won 587 convictions in organized crime cases. Of those convicted, 218 were "syndicate members." By contrast, Webster told reporters at a breakfast meeting here, the government won 515 organized crime convictions in 1981 and of those, only 82 were "syndicate members."

Some 20 to 25 years ago, the FBI's "official view" was that there was no such organization as the Mafia, or La Cosa Nostra. But Webster said, "We've learned a lot since then."

He said the bureau is devoting between 16 percent and 19 percent of its resources in the fight against organized crime. The drive is diffused across the country and, Webster said, it is often overshadowed by "sex and drug" cases and operations such as Abscam. But he said it remains "a very heavy priority and we take it seriously."

On other topics, Webster said proposed revisions in the FBI's "domestic security guidelines" are awaiting review by Attorney General William French Smith.

Webster also defended the handling of a 2 1/4-year-old investigation of a career FBI agent, H. Edward Tickel, which remains unresolved and which Tickel's lawyer disclosed last week. Once the bureau's top expert in court-orderd secret entries and safecracking, Tickel has denied any wrongdoing. But the investigation has been continuing into allegations of tax evasion and other offenses while he continues to work in a nonsensitive position.