If you know which "Requirement" the poll is associated with:
Go to the "Requirement Details" page for that requirement. (How do I do this?). Similarly, you may go to 'Feature Details" or "Use Case Details" page to delete discussions related to those data.
Scroll down to the "Polls" section and find the poll you'd like to delete.
Click edit link next to it to edit that poll.
⚠️ IMPORTANT: Once a user has voted in the poll, the poll can no longer be edited.