Can i get some feedback to my concept please?

I’d guess its a magic attack effect. Its helps to give more context as fx are often heavily influenced by design intent. The glow is too soft with no shape of its own, no noise to it. The color doesn’t transition through the spectrum as it fades, the silhouette of the tail is not that interesting. I’d lean heavier into the arrow head you have there. The curve on the arrow head suggests its not moving very fast, does it need to move fast? I’d add more spark like particles everywhere and maybe some distortion? What type of game is this for? What’s the art style? Why are you making it? All those would help in how to give better feedback.