noun which may take the genitive case particle 'no'
left-leaning; left-wing; leftist
Used to describe people, groups, or ideologies that lean toward the political left. Often used attributively with の.
彼は左翼系の政治家として知られている。
He is known as a left-leaning politician.
その新聞は左翼系の論調で知られている。
That newspaper is known for its left-wing editorial stance.
左翼 is a more general term for 'left wing', while 左翼系 specifically emphasizes the 'left-leaning' or 'leftist' nature.
Compound of 左翼 (left wing) + 系 (system, lineage, type), literally 'left-wing type'.