left wing 
noun (the left wing)
1The radical, reforming, or socialist section of a political party or system.Wales has always had strong left wing and radical political parties and leaders....
- I don't know that anyone is in a position to do that and certainly not the left wing of the Labour Party.
- He's stood for most of what the left wing of the Democratic Party has stood for since 1972.
With reference to the National Assembly in France (1789–91), where the nobles sat to the president's right and the commons to the left
2The left side of a team on the field in soccer, rugby, and field hockey: his usual position on the left wing...
- Zidane took a free-kick from the left wing that curled all the way to the far post.
- Malouda is fouled on the French left wing but Ribery's free kick into the box comes to nothing.
- Some slick passing by Chelsea in midfield releases Frank Lampard down the left wing.
2.1The left side of an army: the Allied left wing...
- Roughly the same time two divisions were sent by Lee to reinforce the left wing.
- The commander of the left wing of the army eyed the approaching enemy formation with interest.
- At Marston Moor, in 1644, he commanded the left wing of the royalist army.
adjective
Radical, reforming, or socialist: left-wing activists...
- Of course socialists should always support left wing officials against the right.
- In the longer term I would hope for a broad left wing alternative to the failed politics of the South.
- It was a mass political event, with a very radical and left wing mood.
Synonyms
socialist, communist, communistic, Bolshevik, leftist, anti-capitalist;
radical, revolutionary, militant, red;
progressive, liberal, reforming, social-democrat, politically correct;
Labour, Labourite;
Marxist, Leninist, Marxist–Leninist, Trotskyite, Maoist
informal, derogatory commie, lefty, pink, bolshie