Answer: playball

AnswerCrossword Clue
PLAYBALLCooperate (with)
PLAYBALLUmp's cry
PLAYBALL1 Down's directive.
PLAYBALLCo-operate.
PLAYBALLCertain opening words
PLAYBALLAn opening line
PLAYBALLDirective
PLAYBALLUmpire's shout
PLAYBALLBook by John Feinstein