trousers/pants for men or women, that are not part of a suit 便裤；宽松的长裤
a pair of slacks
一条便裤
take / pick up the slack
1
use up a surplus or improve the use of resources to avoid an undesirable lull in business抓紧松弛环节, 治理整顿（指将盈余用光或提高资源利用率以避免不良的生意停滞）：
as domestic demand starts to flag, foreign demand will help pick up the slack.
由于国内需求开始萎缩, 外贸需求将有助扭转市场的不景气。
2
pull on the loose end or part of a rope in order to make it taut拉紧松弛的绳索。
slack: work that someone should have done but didn’t do properly or completely
所以：
pick up your slack
= do the work that you failed to do
例句
I’m just here to pick up your slack.
我就是来替你收拾烂摊子 / 补你的工作的。