お代わりする
a substitution for something
the action of making someone act as a substitute for something
a person who substitutes
代わりにこれをください.
Give me this instead.
to substitute something
a thing used for a time instead of the next thing
One thing serves as a substitute for another―serves for another―does duty for another.
to serve for―do duty for―something
a person whose shoulder is leant on by another person, rather than that person using a cane or crutch to lean on