expression, ichidan verb
Idiomatic expression meaning to actively support or take the side of someone, often in a dispute or endeavor. Conveys a sense of lending one's strength or influence.
彼はいつも私の意見に肩を入れてくれる。
He always supports my opinion.
That politician is said to be siding with a particular industry.
expression, ichidan verb
cover one's exposed shoulder again
Original, literal meaning: to put one's shoulder back into a garment that has slipped off. Rarely used in modern Japanese; the idiomatic sense is overwhelmingly more common.
着物の肩がずれたので、肩を入れた。
My kimono slipped off my shoulder, so I pulled it back up.