Possible Clues:

• Why, is that the matter over a boy?
• Why, that's about a bit of the end of 21 across
• This is why one will get to know about one of your family
• That's why it seems to be about your boy
• Think logically about one part of the issue
• That's why it's about a start for 9 across
• Is that why there's something the matter with a boy of yours?
• Crime time forgot? Motive needed
• Think logically about a male child
• Purpose