I could guess these last 3, but would like to now how they're arrived at: 18ac Plants neat kiss with these? (6) O?L?P?. 46d Having to put round Guardian flyer makes us cross (7) T?N?E?O. 52d It may stand in the way, note (4) ?T?T. Thanks
18a - 0xlips. an ox is also called a neat + you kiss with these = lips.
46d - tangelo.It is a cross citrus fruit. the word to put around a guardian flyer = angel.
52d - stet. means let it stand in proof reading terms. note =te inside way = st(street)