lifebuoy

/L AY1 F B UW1 IY0/
noun
  1. 1

    A buoyant object (most commonly torus-shaped) that is used as a life-saving device by keeping a person afloat;

  2. 2

    (metaphoric) Something that rescues one from difficulties.

Source: https://en.wiktionary.org/wiki/life%20buoy, https://en.wiktionary.org/wiki/lifebuoy