'The Entertainer' returns -- this time with Nicol Williamson; The Entertainer. Play by John Osborne. Starring Nicol Williamson. Directed by William Gaskill.

Archie Rice is back in town. For the first time since his New York arrival in 1958, John Osborne's miscreant mummer receives the star treatment in a major production of ''The Entertainer.'' With Nicol Williamson heading the bill at the Roundabout Theater, Archie emerges once more as a second-rate vaudevillian with a phony touch of class, a head full of false hopes, and a desperate determination to survive at whatever cost to those who deserve his love and loyalty.

''The Entertainer'' is a play of eloquent language as well as of intense philosophical commitment. Old Billy Rice (Humphrey Davis), the Edwardian pro of the music halls, expresses Os-borne's salute to a lost elegance and innocence which nevertheless nurtured their own dangerous illu-sions.

In the long first scene of this allegorical tragedy, Billy and his granddaughter Jean (Ellen Tobie) establish a familial entente cordialem that bridges the generation gap through affection. But Jean has spontaneously joined a Trafalgar Square demonstration against the 1956 Suez debacle and is on the point of breaking with her middle-class, career-oriented

suitor. It is Jean who looks on in anger at England's fate and who delivers Osborne's expressions of irony and outrage.

The feckless Archie, meanwhile, moves back and forth between the ghost-ridden seaside resort music hall where his latest show faces disaster and the grubby digs where the Rice domestic drama plays itself out. Archie's stage turn consists of leering plugs for his girlie show, wearily suggestive gags, and would-be pop songs sung with would-be style. The family scenes of bickering, ritual anecdotes, and flippant verbal duels come to focus with the news that Archie's son, Mick, has been taken prisoner in Egypt. Even as he masks his shock over Mick's subsequent murder by his captors, Archie continues scheming recklessly and despicably to rescue his bankrupt stage show.

Mr. Williamson is at his best in the domestic scenes in which the relentlessly articulate Archie, whatever his state of sobriety, conducts his fanciful war of words against particular targets and the world in general. Although he handles the music-hall routines and John Addison tunes with a breezy finesse, there is in this performance an insufficiently sharp distinction between Archie's stage persona and his offstage personality. One cannot help remembering the brilliance with which Laurence Olivier managed the double yet single impression as Archie.

Frances Cuka gives an extraordinarily touching portrayal as Archie's resigned yet loyal wife, a woman who, as she says, has tried to better herself and who now lives in terror of an old age unprovided for. Mr. Davis gives Billy Rice the quiet elegance of an Edwardian pro who remembers a world that was better run, better mannered, and better proportioned. Miss Tobie expresses Jean's awakening awareness with honest intensity. Keith Reddin is both lively and quietly resolute as Frank Rice, the son who has served a jail term as a conscientious objector.

The company directed by William Gaskill includes Richard M. Davidson (Archie's generous brother), David Brunetti (pianist-conductor of the onstage trio), and Elizabeth Owens (the ''Gorgeous Gladys'' of a momentary behind-scrim tableau). Michael Sharp designed the scenery, A. Christina Ciannini the costumes , and Barry Arnold the lighting.