Have you been prescribed only Clonotril and no other drug? If yes, I would suggest you to visit your Psychiatrist and ask him to write another drug which you can take half and hour or so before your performance (since Performance Anxiety is a part of Anxiety Disorder, and it seems you may be having Social Anxiety). If you have been having Anxiety Disorder since a long time, I feel you should be prescribed an SSRI, a Beta Blocker and a Benzodiazepine (like Clonotril). Discuss this with your Psychiatrist.
Next Steps
Remember, the SSRI is long term (for 4-6 months at least), and meant to actually try to cure you of your Anxiety Disorder. Benzodiazepine is for quick relief and supplements SSRIs. Beta Blockers are also for immediate relief, especially in Anxiety Disorder. SSRI is actually the main drug, you may say!
Health Tips
Do not try to self medicate! You won't get these medications without prescription and you surely don't know which doses will work for you, so first consult your Psychiatrist. It seems you haven't actually consulted a Psychiatrist and Clonotril was prescribed by a doctor of some other discipline. I hope I am wrong!