slack up

Related to slack up: slack off

slack up (on someone or something)

1. To release or ease the tension or pressure (on something). I'll need to slack up a bit so that I can adjust the rigging. Make sure you don't slack up on those harnesses before we've come to a complete stop.
2. To stop doing something as intensely or frequently. I think you should slack up on the drinking, Bob. If we slack up now, we'll never meet our sales quota for the quarter.
3. To stop being so critical of or putting so much pressure on someone. Would you slack up already? I know I messed up the account, so I don't need you berating me for it any further. Slack up on Samantha, she's under a lot of pressure at home.
See also: slack, someone, up
Farlex Dictionary of Idioms.

slack up (on something)

 and slack off (on something)
to release the pressure or tension on something. Slack up on the rope a bit, will you? Please slack off!
See also: slack, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • slack up (on someone or something)
  • slack off
  • slack off on (something)
  • slackmaster
  • slack master
  • take up the slack
  • pick up the slack
  • cut someone some slack
  • cut someone some slack, to
  • take the slack up