14 does end in "y", unaltered after the exchange. There are 2 similar expressions used; both with the same "2nd part" so it might not be the first to come to your mind.
I am complete except that I still cannot crack 13, despite having deducted the 2 words. I also seem to have only 9 treated solutions - and I had 22 across - think there is a spare word in 30 but can't find the connection ...