Demotion, Degradation, Demolish
noun, verbal noun
Usually if you're going to the left in Japanese, it's not a good thing. So if you transition to the left it's seen as a demotion. Going to the right is way better.
させん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
田舎の支店に左遷されました。
I was demoted to a branch store in the country.