Complex sentence: As a child actress, Clare Sandars was given uncredited parts in two films, but notably appeared as Mrs. Miniver's daughter Judy in "Mrs. Miniver", where she played Mendelssohn's "Wedding March" on the piano for the family.
Split into simpler sentences: As a child actress, Clare Sandars notably appeared as Mrs. Miniver's daughter Judy in "Mrs. Miniver". There is a scene in "Mrs Miniver" where she plays Mendelssohn's "Wedding March" on the piano for the family.