mainstay
Concise Oxford English Dictionary © 2008 Oxford University Press:
mainstay/ˈmeɪnsteɪ/
▶noun
- 1 a stay which extends from the maintop to the foot of the foremast of a sailing ship.
- 2 the chief support or basis: sugar is the mainstay of the island's economy.
'mainstay' also found in these Oxford entries:

