wolf at the/(one's) door
1. A creditor or moneylender looking for repayment. I've had the wolves at my door ever since I took out that idiotic payday loan a year ago. With so many wolves at our door, I think I need to get a better paying job soon.
2. Any impending or imminent source of danger, disaster, or ruin. This market trend is becoming wildly unsustainable and erratic, and this wolf at the door could threaten to plunge us into another recession. That country is not our ally—it is a wolf at our door, waiting for its opportunity to strike.