lifesaver
n. B1 Intermediate US //ˈɫaɪfˌseɪvɝ// UK //lˈaɪfseɪvɐ// life·saver
n. something that helps you survive or solves a very difficult problem. You use this to describe a person or thing that is extremely useful in a dangerous or stressful situation.
n. a person or thing that provides essential help or relief in a critical situation. Often used figuratively to describe a solution to a significant problem.
The new software was a lifesaver for our busy team.
When the car broke down on the highway, the roadside assistance service was a lifesaver for the stranded family.
The discovery of the ancient manuscript proved to be a lifesaver for the historian, providing the missing evidence required to complete her decades-long research project.
From life + saver.