Answer:

TETRAD

Answer	Crossword Clue
TETRAD	Foursome
TETRAD	Four-part structure
TETRAD	Quartet

TETRAD	Any foursome
TETRAD	Monopoly's railroads, e.g.
TETRAD	Four-note chord
TETRAD	Group of four
TETRAD	Four of a kind
TETRAD	The classical elements, e.g.
TETRAD	Brahms' symphonies, e.g.
TETRAD	The number four.

TETRAD	Collection of four.
TETRAD	Four.
TETRAD	Group of four.
TETRAD	Quaternion.
TETRAD	Chord.
TETRAD	Fourfold
TETRAD	The women in "Little Women," e.g.
TETRAD	Cat's paws, e.g.

TETRAD	Half of an octet
TETRAD	Golf group often
TETRAD	Trio plus one
TETRAD	The Horsemen of the Apocalypse, e.g.
TETRAD	Gift of calling birds, say