OK, I had a 1 letter addition to the 5ac clue that I wasn't happy with, but completed one of the categories. I see now there's a 2 letter addition which works much better, and will complete the other category.
I have a two letter addition to 5A(clue) of a category where they are all of two letters - still have another category with 4 of one letter and one of two....if that makes sense?