Not a difficult crossword and therefore stuck.
27ac, 'The actor playing Moses, for example' (8), ?H???E?T;
23dn, 'Idol's present, best possible person'(4,4), ???S ?I?T;
21ac, 'Clue could be perfect, if shortened' (4), ?R?A;
55ac, 'Go away for test', (3,3), ?R? O?T. TRY OUT?