1d answer from clue wordplay ...miscreant ... anagram of nacre moist ...extra is O.
Theme ...remove the m(money) anagram it and you get cisterna to fit in your grid.
16d from the word play ...triggerman(y) Y is extra ... remove the M ... angarm t and you get regrating for the grid answer
The other 7 themed ones are 1a, 42a, 6a, 18a, 26d all following the same procedure as above.
37a and 15d are also themed but don't change