[angvelem]

Примерно так:

Код:

  TForm1 = class(TForm)
  ...
  public
    procedure MemoClear;
  end;

procedure TForm1.MemoClear;
begin
  memo1.Clear;
  memo1.Lines[0]:='парам';
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  MemoClear;
end;