mainstay
1. [ noun ] a central cohesive source of support and stability
Synonyms: backbone anchor lynchpin keystone linchpin
Examples:

"faith is his anchor" "the keystone of campaign reform was the ban on soft money" "he is the linchpin of this firm"

Related terms: support anchor
2. [ noun ] a prominent supporter
Synonyms: pillar
Examples:

"he is a pillar of the community"

Related terms: supporter
3. [ noun ] (nautical) the forestay that braces the mainmast
Related terms: forestay
Similar spelling:   mainmast
  mainsheet
  mainstream