illustrator has the ability to copy assets directly from your workspace into photoshop. it'll give you a choice of what to paste them as (i usually pick sharp objects, since its essentially acts as a vector graphic)
thats probably not the most efficient way to do it, but if push comes to shove, just copy/paste your layers from illustrator to photoshop
whoops misread you. if its line drawing you wanna tidy up, the same method applies just switch programs. copy your layers from photoshop into illustrator. if the transparency doesn't carry over, you can just auto trace the image, ungroup/"explode" the lines, and then you can delete whatever the background is accordingly
again its probably not the most efficient way, but its quick and it always gets the job done for me
EDIT: correct me if im wrong, but it also sounds like you're trying to manipulate a photoshop file in illustrator (as in, editing lines made in photoshop like you can in illustrator) photoshop is pixel based, and illustrator is vector based. as far as i know this cant be done because illustrator doesn't automatically convert pixel to vector. its a totally different kind of image. you'd just have to trace it or auto trace it
