Looks like that connection is a glued joint, and there is no repair for that. It will have to be cut out, new pipe splice in. It appears that the bushing at the inlet to the manifold is also glued. If so, you have major assembly rebuild on your hands.
This was a nice neat manifold assembly , and the drawback to building it that way, instead of sprawled out.!!....is that repairs are a big deal.
edit: After taking a second look at the photo, I realize the leak is between two manifold sections. That leak spot you point to may not be a joint at all. It may be crack in the fitting itself, if it is leaking exactly at the tip of your arrow. If it is just to the left of the arrow, that appears to be a glue joint between two sections of premade manifold, and it will not be repairable. Gonna need a fistful of fittings and rebuild this whole thing!