Possible Clues:

• Tricky fellows pitch a tent in seconds
• Mischiefmakers
• Works perfunctorily, frauds netting tiny amount
• Incorrigible fellows
• April foolers, e.g
• Mischievous children
• Monkeys: small groups of like-minded individuals
• Rogues sleep under canvas on board ship
• Imps, rascals
• Mischief-makers and saints outside military establishment