Possible Clues:

• "___ time" (boss's dictum)
• "— your best behavior"
• '___ your toes!'
• "___ the lookout!"
• "Just to ___ the safe side ..."
• '___ your best behavior'
• Words before guard or time
• 'Just to -- the safe side ...'
• "___ the lookout!" (2 words)
• '___ the alert!'