Dick Stockton, young again at 35, already has won one of the two tournaments on the Prudential-Bache Securities Grand Champions tour he has played this season. If he can survive the heat and a field of 11 other 35-and-over professionals in the Grand Champions $40,000 Washington tournament, beginning today on the clay courts at Rock Creek Tennis Stadium, he could make it two for three in the final Monday night.

"I've always done pretty well on clay," Stockton said. "It's a real good field, though. And all our tournaments are so wide open, I don't think anyone can dominate."

Round robin play in singles and doubles begins today at 6 p.m. for the field, which also includes Stan Smith, Jaime Fillol, Colin Dibley, Sherwood Stewart, John Alexander, Ross Case, Steve Krulevitz, Andrew Pattison, Manuel Orantes, Ray Moore and defending champion Cliff Richey. To qualify for the Grand Champions tour, a player must have won a Grand Slam tournament, played for his country's Davis Cup team or achieved the No. 1 ranking in his country.

Round robin play continues Friday and Saturday, with the winner from each of the four groups advancing to Sunday's semifinals. The singles final is set for Monday at 7 p.m.

Although Stockton is a good clay court player, several others in the tournament -- Richey, Fillol and Orantes -- are particularly noted for strong performances on slow courts. In the first tournament on the tour this year, which was played in Sarasota, Fla., on clay, Richey edged Fillol in a third-set tie breaker for the win. Stockton won his title on hard courts over Dibley in Atlanta.

"There's a lot of really good clay court players coming," Stockton said. "A lot will depend on the weather and how well the players hold up to the heat."

Fans can expect little drop in the quality of tennis in this tournament compared to the Sovran Bank/DC National Tennis Classic that begins Monday, according to Stockton. "In a lot of ways, I think the caliber of play is just as good because the players have kept themselves in shape," he said. "They are conscientious about their tennis, and not just out for a laugh.

"I think it may be even better spectator tennis, because we take our time about coming into the net and set up more rather than a serve, a volley and that's it. I think the average fan can identify more with that."

"These over-35 guys are still playing hard," said Smith. "And there are still some rivalries out there between the players, although they are not quite as intense as they once were."

Ticket prices for the five days of play range from $6 today to $9 for Monday's final, and are on sale at all Hecht's department stores and TicketCenter locations. Today's Matches Stadium Court

Jaime Fillol vs. John Alexander; Cliff Richey vs. Steve Krulevitz; Ross Case-John Alexander vs. Andrew Pattison-Ray Moore. Court A2

Manuel Orantes vs. Andrew Pattison; Dick Stockton vs. Ray Moore.