Amateur Hour definition

Probably from the name of a series of US radio and television programs showcasing the talents of amateur performers.

A situation or activity in which the participants show a lack of skill, sound judgment, or professionalism.
- 2007, David von Drehle, "Will Rudy's Get-Tough Image Backfire?,"Time, 21 Jun.,
  
  "It's the kind of foul-up that suggests that his campaign team isn't functioning as well as it should," the G.O.P. source said. "Presidential campaigns are not the time for amateur hour."