stand in for

stand in for (someone or something)

To be or act as a substitute for someone or something; to do something in someone's or something's stead. It was decided that I would stand in for my sister at the head of the company while she took her sabbatical. Because of my diet I have this low-calorie spray standing in for olive oil while I cook, but it's just not the same. We stand in for the actors so the crew can light the set properly.
See also: stand
Farlex Dictionary of Idioms.

stand in for

Substitute for, as in He's kindly agreed to stand in for me at the reception. [Early 1900s]
See also: stand
The American Heritage® Dictionary of Idioms by Christine Ammer.

stand in for

v.
To act as a substitute for someone or something, especially for an actor while the lights and camera are adjusted: The understudy stood in for the lead performer.
See also: stand
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • all right
  • (someone or something) promises well
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • (have) got something going (with someone)
  • a straw will show which way the wind blows
  • accompanied by
  • accompanied by (someone or something)
  • accompany
  • a crack at (someone or something)