Possible Clues:

• A drug problem hounds those working on leads in the security business
• Keep an eye on the boxers for safekeeping
• What 9, 10, 11, 15, 17, 25, 26, 27 Across and 1, 3 Down do for means of defence
• Dobermans and mastiffs, traditionally
• Dobermans, often
• Great Pyrenees, for example