In the surface of clay who was the opponent in the game resulting in a score of 6–4, 6–4?
CREATE TABLE "itf_singles_finals_19" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent_in_the_final" text,
  "score" text
);
SELECT "opponent_in_the_final" FROM "itf_singles_finals_19" WHERE "surface"='clay' AND "score"='6–4, 6–4';