mainstay in WordNet English dictionary

1. a central cohesive source of support and stability
   "faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
   anchor  mainstay  keystone  backbone  linchpin  lynchpin 
   
2. the forestay that braces the mainmast
   mainstay 
   
3. a prominent supporter
   "he is a pillar of the community"
   pillar  mainstay