LET v.
the passive sense; as, let make, i. e., cause to be made; let bring, i. e., cause to be brought. [Obs.] This irous, cursed wretch Let this knight's son anon before him fetch. Chaucer. He . . . thus let do slay hem all three. Chaucer. Anon he let two coffers make. Gower.
LINE n. 2 definitions
Course of conduct, thought, occupation, or policy; method of argument; department of industry, trade, or intellectual activity. He is uncommonly powerful in his own line, but it is not the line of a first-rate man. Coleridge.