This speaks of Jeremiah being unaware of his enemies' plans to kill him by comparing him to a lamb who is being led to be slaughtered. (See: [[rc://en/ta/man/jit/figs-metaphor]])
Here Jeremiah's enemies speak of killing him as if he were a fruit tree that they were planning to destroy. (See: [[rc://en/ta/man/jit/figs-metaphor]])
The phrase "cut him off" means to destroy him. Also, "the living" refers to living people. Alternate translation: "Let us kill him so he is no longer in the land of those who are alive" or "Let us destroy him so that he is no longer among the world of living people" (See: [[rc://en/ta/man/jit/figs-idiom]])