What is the surface of the score, 7–6 (7–3) , 6–3?
CREATE TABLE "singles_2_3" (
  "outcome" text,
  "date" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "surface" FROM "singles_2_3" WHERE "score"='7–6 (7–3) , 6–3';