Possible Clues:

• Way of training students variously in production of opera taking year
• Act with old student in show again
• Be someone you're not
• Most of those in 23 down with work in the abbey employ a therapeutic technique
• Acting out situations in rep – loyal characters changing places
• Train dramatically let off steam after rumble heard
• Do some therapeutic pretending
• Not be oneself, but rather be one's elf?
• Job for those in 21 down is character building
• Head off clear ploy to train acting in character?