This is one of Cleary's intrigues which, while it takes place on foreign soil, is also on familiar ground--this time Beirut, just before the Arab-Israeli blowup. Involved there are a good many mixed nationals, who except for the occasional haberdashery--a Brooks Brothers suit or a St. Laurent scarf--might be hard to identify since Mr. Cleary doesn't do much about his characters. But he's an eager plotter and this one concerns (a) Paul Tancred at the American Embassy, (b) his mistress, half French, half Arab; (c) his father who presumably deals in diamonds and (d) an old prison camp acquaintance, a bogus Britisher attempting to find a buyer for his shipment of arms, any buyer. . . . Mark Cross attache case with a competently processed brief.