The threat of poverty or starvation
This phrase comes from a time when people living in wilderness or less-populated areas feared wolves a great deal. People who knew little about wolves and were therefore superstitious about them believed that when a person was weak or helpless or let down their guard, wolves would race in from the shadows and kill them, merely because they were unable to defend themselves.
Eventually, saying, “the wolves are at my door” meant that the person was destitute, poor or hopeless, and all but waiting for death to take them. The meaning has become more casual over time, and now we might use it if we’ve lost a job, or are broke. If someone said, “I lost my job two months ago and already the wolves are at my door,” it would mean that they feel depressed or are in serious financial trouble.
The phrase may also be used to ask how a person is doing. For instance, “What have you been doing to keep the wolves from your door?” It’s the same as asking, “so what are you up to these days?” A person would just be asking for a general update on what’s going on in the other person’s life.
I wouldn’t mind having a real wolf at my door. If it was tame, that is!