How to make the offset path to cut the back object in illustrator

I created a layer (object) and on the front ive put arrow across the object. I used a offset path to make a gape betwin the back object and the arrow that in the front.

the offset path is white and its goos when the background is white, BUT not in other background colors because you can see the white gap (offset path).

Im need the path to be transparent OR any option to cut the back layer with the offset path. I used this toturial: https://www.youtube.com/watch?v=qapO4aVqITI