Depending on the venue, you may be able to remove the heckler. If the heckler is also a competitor, then that would be grounds for disqualification. Beyond that, there really isn't much you can do. It all depends on the where and the situation. One would hope that members of an audience would have enough common courtesy to be respectful of someone competing, but that isn't always the case, and as a performer, you need to be prepared for that eventuality.
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"I hold the key to an open door....will I ever be free...?"