'standby'
You would be well within your rights to tell your instructor that he/she is being anal and needs a social life.
Clearances need to be read back in order to confirm understanding. Standby is not a clearance. If an ATC said "ABC, you are cleared to beat the snot out of the analy retentive moron next to you and standby for a new instructor" - you'd have to read that back....😜