Answer:

major

Answer	Crossword Clue
MAJOR	Undergraduate's declaration
MAJOR	Something a college junior has that a freshman usually doesn't
MAJOR	Principal

MAJOR	One of four on the annual tennis calendar
MAJOR	Sophomore's choice
MAJOR	Lowest field rank
MAJOR	Epic
MAJOR	College concentration
MAJOR	College student's concentration
MAJOR	Biology or English
MAJOR	Big-time

MAJOR	Paramount
MAJOR	See 3-Down
MAJOR	Huge
MAJOR	Student's declaration
MAJOR	Blair's predecessor
MAJOR	Prominent
MAJOR	Declaration of education
MAJOR	See 53-Across

MAJOR	Kind of key
MAJOR	Kind of party
MAJOR	... medical
MAJOR	Captain's superior
MAJOR	College choice
MAJOR	Base V.I.P.
MAJOR	Like some parties
MAJOR	College declaration

MAJOR	Word before league or domo
MAJOR	Thatcher's successor
MAJOR	... Barbara
MAJOR	Hoople or Houlihan