Righthander Jeff Reardon, who was instrumental in the Minnesosta Twins' 1980 World Series championship and also pitched for the Red Sox from 1990-92, was arrested in Florida yesterday on suspicion of committing armed robbery. According to a release from the Palm Beach Gardens Police Department, Reardon, 50, entered a jewelry store in a shopping mall and handed a clerk a note demanding money. The clerk, believing he had a gun, filled a bag with an undisclosed amount of cash. Reardon fled with the cash and was followed by the store manager and arrested outside a restaurant, police said .