a field day

The freedom or an opportunity to do a lot of something one wants. (Often, news outlets are said to be "having a field day" if they are criticizing someone.) The press is going to have a field day if this story gets out. Our team has been having a field day going over all the information the study produced.

field day

A time of great pleasure, activity, or opportunity, as in The press had a field day with this sensational murder trial. This colloquial expression, dating from the 1700s, originally referred to a day set aside for military maneuvers and exercises, and later was extended to a similar day for sports and games. Since the early 1800s it has been used more loosely.