what software are you using to run the loops?

try switching the lines and see if the Loop Channel takes the buzz and the click line ends up clean. if that is the case, it's a bad cable or snake input.

Headphone output jacks are inherently noisy. You should consider using an inexpensive interface with balanced outputs. Another trick you can do is gate your click track so that only the click passes through the channel and the noise is gated out. Obviously it is best to not have noise at all, but I have found this to work well in a pinch. Ultimately it is a temporary fix because you want to figure out where the noise is coming from and get rid of it.

behringer = :(
that thing might give you a hum instead of remove it. :)

if you connect headphones to the jack and you aren't getting noise, then there is something in the chain from the laptop to the sound board.
check all cables by replacing them one at a time.
check any DIs. flip ground switch.
if it's a long cable, make sure it's balanced correctly. (make sure you're using a DI and an XLR)
check to see if there are any power cords running parallel to your signal.
is there anything on the same breaker interjecting noise (lighting specifically will add a ton of noise)