3:6 What does "the letter killeth but the Spirit giveth life" mean?.
3:6 What does "walking disorderly" refer to here?
Walking disorderly here has to do with refusing to work to keep one's self. Some of the Thessalonian Christians refused to work and were taking advantage of the generosity of the church to feed them.
Paul commanded the church to stop supporting them and also to disfellowship them, but at the same time not to stop supporting those truly in need (CP V7-15).