Who was the opponent in the math that was played in Nice on a clay court?
CREATE TABLE "singles_7_titles_8_runner_ups" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "opponent" FROM "singles_7_titles_8_runner_ups" WHERE "surface"='clay' AND "tournament"='nice';