What is "to act for"

Act \Act\, v. i.

1. To exert power; to produce an effect; as, the stomach acts upon food.

2. To perform actions; to fulfill functions; to put forth energy; to move, as opposed to remaining at rest; to carry into effect a determination of the will.

   He hangs between, in doubt to act or rest.
   --Pope.

3. To behave or conduct, as in morals, private duties, or public offices; to bear or deport one's self; as, we know not why he has acted so.

4. To perform on the stage; to represent a character.

   To show the world how Garrick did not act.
   --Cowper.

   To act as or To act for, to do the work of; to serve as.

   To act on, to regulate one's conduct according to.

   To act up to, to equal in action; to fulfill in practice; as, he has acted up to his engagement or his advantages.

   to act up, to misbehave