I know I'm late posting, only finished this morning.
In terms of a theme does the following count:
In two groups of 3 clues apply the following rule:
If M and W are interchangeable (maybe because of 13) and you can change one letter then the first answer will be an anagram of the next.
4->7->17 and 2->19->23?
Would have liked to tie 9 in but can't