If that edge that's visible in your image is because it's the edge of your smoke element you're going to have to find (or film) a different smoke element. There's no way you're going to be able to realistically recreate a smoke element to match that.
It is possible to create realistic smoke, but next to impossible to create realistic smoke that not only looks like, but matches AND continues the motion of existing smoke footage. No way.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.