City construction projects (improvements or units) can be hurried to completion if necessary. Use the "Hurry" button on the City Display.
Under Despotism and Communism you hurry production in your cities by forced labor. Disillusioned by your harsh rule, citizens will leave your city if you institute this type of rushed production.
Under Monarchy, Republic, and Democracy you can pay overtime and hire temporary workers to complete a project. This costs gold from your treasury; the amount depends upon how much work remains to be done.
Leaders can also be used to hurry production.
You have no production if your civilization is in Anarchy.