mainstay
source sentence: "On the Web, students can also find electronic versions of the most popular academic journals, the mainstay of research for faculty and advanced students."
context clues: indirect definition clues, inference clues, (syn.) leader, (ant.) unimportant
definition: person or thing that acts as a chief support or part
original sentence: During the American Revolutionary War, Tea was thought to be the mainstay of the economy.
http://dictionary.reference.com/browse/mainstay
