lifeline
n.something that helps you survive or succeed when you are in a very difficult situation. It can be a person, a service, or a piece of equipment that saves you.
n.a source of vital assistance or support that enables survival or continued operation during a crisis. In its literal sense, refers to a rope or line used for saving life at sea.
“The government grant was a lifeline for the small business.”
“For many elderly residents living in remote areas, the local bus service is a vital lifeline to the nearest pharmacy.”
“The emergency credit facility provided a necessary lifeline to the bank, preventing a total collapse of liquidity while the board negotiated a more permanent restructuring plan.”
Often used metaphorically with the preposition 'to' or 'for'.
“The ferry served as a vital lifeline for remote fishing communities along the lake, connecting them to food supplies, markets and essential services.”
“Many survivors told me they consider the organization’s semiannual conferences to be a lifeline.”
From life + line.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.