The Baltimore Orioles, in conjunction with Purina, will hold a clinic for youngsters ages 6-13 Saturday at the Dallastown (Pa.) Community Park near York, Pa. Scheduled to appear from the Orioles are Jeff Ballard, Tim Hulett, Elrod Hendricks and Tom McCraw. All youngsters attending the clinic will receive an Orioles/Purina baseball cap. For more information, call 243-9800.