understudy
verb (used with object)
to learn (a role) in order to replace the regular actor or actress when necessary.
Used to describe an ongoing action or state that is currently taking place in the immediate present.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Mr. Taylor said that when Mr. Novak is understudying a dance, he will have Mr. Novak sit next to him in the studio to hear his comments.
From New York Times ● May 18, 2018