Possible Clues:

• 'Have the wit, by the sound of it, to have little money up your nose in the ship (6)'
• Hints for hounds
• Unseen air travelers
• By the sound of them one knows to get the meaning of them
• Bloodhound pickups
• Odours
• Gets wind of American cash being loaded on board ship
• Knows how to get such intelligence, by the sound of it
• Sounds as if one knows how to get a little money from the South
• 'One knows how to make sense of them, by the sound of them (6)'