mainstay

noun3

1. •
   A chief support.

   • Agriculture is the mainstay of this country’s economy.
2. •
   Someone or something that can be depended on to make a regular contribution.

   • The marina was a mainstay of the neighborhood, and Mr. O’Rourke was known for staging salsa and merengue concerts. — 2007
3. •
   A stabilising rope from high on the mainmast to the base of the foremast.