sickle
鐮 centers on a sickle, a curved metal blade used for cutting crops or grass.
鐮 combines 金 (metal) with 廉, which likely contributes the sound. The character is a phono-semantic compound for a metal sickle.
The left side 金 is metal, and the right side 廉 looks like a curved blade with a handle. Picture a metal sickle cutting through a field.
For レン, imagine a sickle cutting through a field of lentils: lentil -> レン, and the metal blade harvests them.