ok, ive got started on this, and got stuck

after much strugle getting the bolts out that were very rusted, i started to drop the axle, but can only get it to drop about an inch, i think i see the problem, but havent any idea how to sort it so any help welcomed.

this shows how far im able to drop the axle.

what i think it is is this...

what looks like a break line, however i see no way to unclip it? ive uncliped the one that runs under the axle bush, but i think this line is stoping me droping it further, any idea of how to unclip it???
cheers