Answer:

spitball

Answer	Crossword Clue
SPITBALL	Diamond offense
SPITBALL	Illegal pitch
SPITBALL	Illegal diamond pitch

SPITBALL	Schoolboy's missile.
SPITBALL	Outlawed baseball pitch
SPITBALL	Schoolroom missile
SPITBALL	It's hard to hit
SPITBALL	Changing pitch
SPITBALL	Classroom missile
SPITBALL	It uses liquid from a pitcher
SPITBALL	Wet missile

SPITBALL	Misbehaving student's missile