1a A great deal, reduced green fruit (5) M?N?O
mango - green fruit ??
13d daily Express leaders having various details of least interest (9)
D?A?L?E?T deadliest fit sthe parse of DE + anagram of details , but doesn't really mean of least interest??
17a Editor's job, concealing Democratic opposition to political change (8)
R?A?T?O? reaction fits ?