Someone who puts on a show for the entertainment or enjoyment of others.
A person who entertains others, esp. as a profession, as a singer, actor, presenter, dancer, musician, magician, comedian, etc.
A performer who understudies; a standby.
To act as an understudy (to someone).
To study or know a role to such an extent as to be able to replace the normal performer when required.
To act in a similar manner to some known person.