A writ by the clerk commanding a peace officer to bring a witness before a court is known as a ____________.

The term that describes a writ issued by the clerk commanding a peace officer to bring a witness before a court is a writ of attachment. This type of writ is utilized to compel a person to appear and provide testimony in court. It ensures that the presence of the witness is secured, which is essential for the judicial process. The role of the peace officer in this instance is to enforce the court's mandate, ensuring that necessary witnesses are available to contribute to the case being heard.

In contrast, a writ of habeas corpus is primarily concerned with the right to seek relief from unlawful detention, whereas a writ of certiorari is a higher court's order to review a lower court's decision. A writ of injunction, on the other hand, is used to order a party to do or refrain from doing specific actions. Each of these other writs addresses different legal circumstances, which is why they do not fit the definition required in the question.