THE NUTTY NUT, with Stephen Kearney, Stella Stevens, Robert Trebor and Peter Lupus. Directed by Adam Rifkin. At select UA and Broadway circuits. GIVEN that local taste in comedy tends toward the slapstick, there must be at least a chance of The Nutty Nut doing well here; not much of one though. The Nutty Nut is a mishmash of visual jokes, hardly any of them amusing, held together by an overly contrived plot. After half an hour it becomes obvious that what is on the screen is little more than a badly conceived mixture of the worst of Benny Hill,West End farce and the kind of British sit-com that involves a Swedish au pair, a wife, a pair of trousers and a vicar. The Nutty Nut' s lead is taken by Stephen Kearney, a little-known Australian comedian of dubious talent. The script is laboured, tired, cliche-ridden, essentially unfunny, and some of the ''jokes'' are in very bad taste. The sight of a blind chef about to roast a baby he believes to be a chicken might have been funny in the hands of the Monty Python crew, but left to director Adam Rifkin, it is just distasteful. The film's threadbare plot centres around the two Nut twins: one has been committed, one has gone into politics. Nathan (the nutty Nut) has a multiple personality disorder. Sometimes Nathan is a dog, a cabaret singer, a cowboy, a transvestite, a clown - the list goes on and on, yet incredibly, not one of these characters is funny.