18. never first (6,3) n?m?e? ???
28. say it twice, then read all about it! (5) o???a
The first letter of the second word in clue 18 is the third letter of clue 28.
9. Old McDonald's place of business (4,4) ???m ?a?d
11. an odd amount for the unusual one (3,3) o?d ??? o?t
I think no. 9 is "farm yard" and no. 11 is "odd one out" but the second letter of the first word of clue 9 is the the second letter of the second word of clue 11.
Maybe there's a mistake with the crossword