Who is the opponent when the score was 6–4, 6–2 and the surface was clay?
CREATE TABLE "singles_18_5_13" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "opponent" FROM "singles_18_5_13" WHERE "score"='6–4, 6–2' AND "surface"='clay';