lifeline
Something that gives crucial help or keeps you safe.
A lifeline is something that keeps you safe, alive, or connected when you're in danger or difficulty. The word originally meant a rope thrown to someone drowning in water, giving them something to grab onto while being pulled to safety. Emergency workers still use actual lifelines: mountain climbers attach safety ropes, and firefighters use safety lines when entering dangerous buildings.
The word has grown to mean anything that provides crucial help or support. When a struggling business gets a loan that saves it from closing, that money is a lifeline. When you're stuck on a hard homework problem and your older sister explains the concept you were missing, her help is a lifeline. During tough times, a friend who listens and cares can be an emotional lifeline.
In game shows, a lifeline is a special help option contestants can use when they don't know an answer, like calling a friend or eliminating wrong choices. Notice how the word carries the sense of something you can depend on when things get difficult, something that connects you to safety or help when you need it most.