Some help with the following, please:
19A Lengthening words in impressive short essay(9): ??????SI?
DOWN:
12 Apostle more into transgression(5): ?I?O?
16 Puzzling magician let loose(11): ??????T????
25 Mid-September bookish husband cut wheat(7):??N????
27 Salt from UKnavy stands in for tenor(7): ?R?N???
31 Splendour of our flag(not one flapping)(6): F?L???