Possible Clues:

• Gave lessons, reportedly tight
• Jeer with any number leaving stressed
• By the sound of it, worked in education, far from relaxed
• Greek character tense and strained
• Tense, as is pupil in audition
• Like a tightrope, more so than a slackline
• Opposite of relaxed
• Like a tug-of-war rope
• At a breaking point, maybe
• Like a suspenseful thriller