The phrase "lean times" refers to periods when there is a lack of money, resources, or prosperity. It means experiencing financial difficulty or scarcity. Full definition
In leaner times engagement was viewed as a cheap way to replace the salary and benefits they were cutting. (blog.simplyhired.com)
We've been at it for 3.5 years and things are going really well, but you should plan for lean times in the early years. (slaw.ca)
But they think maybe it was a way our body evolved to use vegetables to help preserve energy during lean times in our ancient past. (nutritionfacts.org)