When he didn't get the pay raise he was expecting, he had to take another job to 'pick up the slack'. [=to make up for the money he was not making]
The manager has to 'take up the slack' when employees don't do their jobs correctly.
We left some 'slack' in the budget so that we can hire more people if we have to.
(..) He's an out-of-work actor living in a share house. And he drives a Series BMW. Tori, l really think that you need to cut Heath a little bit of slack. His aunt died three years ago and he really needs new headshots. He's just going through a really rough time right now. Okay? You okay? (..)2004 White Chicks