What is "to come into play"

Play \Play\, n.

1. Amusement; sport; frolic; gambols.

2. Any exercise, or series of actions, intended for amusement or diversion; a game.

   John naturally loved rough play.
   --Arbuthnot.

3. The act or practice of contending for victory, amusement, or a prize, as at dice, cards, or billiards; gaming; as, to lose a fortune in play.

4. Action; use; employment; exercise; practice; as, fair play; sword play; a play of wit. ``The next who comes in play.''
   --Dryden.

5. A dramatic composition; a comedy or tragedy; a composition in which characters are represented by dialogue and action.

   A play ought to be a just image of human nature.
   --Dryden.

6. The representation or exhibition of a comedy or tragedy; as, he attends ever play.

7. Performance on an instrument of music.

8. Motion; movement, regular or irregular; as, the play of a wheel or piston; hence, also, room for motion; free and easy action. ``To give them play, front and rear.''
   --Milton.

   The joints are let exactly into one another, that they have no play between them.
   --Moxon.

9. Hence, liberty of acting; room for enlargement or display; scope; as, to give full play to mirth.

   Play actor, an actor of dramas.
   --Prynne.

   Play debt, a gambling debt.
   --Arbuthnot.

   Play pleasure, idle amusement. [Obs.]
   --Bacon.

   A play upon words, the use of a word in such a way as to be capable of double meaning; punning.

   Play of colors, prismatic variation of colors.

   To bring into play, To come into play, to bring or come into use or exercise.

   To hold in play, to keep occupied or employed.

   I, with two more to help me, Will hold the foe in play.
   --Macaulay.