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.
(..) - I have no memory of this beaver. - He's an otter, actually. - He was here a couple of Wednesdays ago. Remember? - No. - Yeah, he was wearing a green cable knit sweater vest, and a new pair of Quarterway slacks. Oh, and a Paisley tie, sweet Windsor knot. - Real tight. Remember that, Nangi? - No. (..)2016 Zootopia