Choker

noun

1. A piece of jewelry or ornamental fabric, worn as a necklace or neckerchief, tight to the throat.
2. One who, or that which, chokes or strangles.
3. One who operates the choke of an engine during ignition.
4. Any disappointing or upsetting circumstance.

   "I lost £100 on the horses today — what a choker!"

5. One who performs badly at an important part of a competition because they are nervous, especially when winning.