To act for

Act Act, v. i. 1. To exert power; to produce an effect; as, the stomach acts upon food. [1913 Webster]

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. [1913 Webster]

He hangs between, in doubt to act or rest. --Pope. [1913 Webster]

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. [1913 Webster]

4. To perform on the stage; to represent a character. [1913 Webster]

To show the world how Garrick did not act. --Cowper. [1913 Webster]

{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 [1913 Webster]