Need Help! Is the Elf Ranger simply the most OP thing ever?!

I'm hosting my first session of Dungeon World and we are having a great time, but some controversy came up during play. One of my players is playing the Ranger class with no hacks or anything. His race is elf as well. The passive for the Elf Ranger says that "When you undertake and perilous journey through wilderness whatever job you take you succeed as if you rolled 10+". I'm confused about the wording, does this mean that they always roll 10+ on the Perilous Journey Move or do they succeed at everything involved on the mission. For example my player wanted to track and kill a bear in the woods constituting a perilous journey through the wood. Does the Elf Ranger passive mean that he also rolls 10+ on all his combat rolls against the bear as well?   

No, it's just a 10+ on whichever of the three (four? I forget) jobs that are part of the "Undertake a Perilous Journey" move. Perilous Journey is a "combined" move, where each of several players takes on a specific role to help the party get from point A to point B. The Elf Ranger simply gets an auto 10+ for his contributing roll to that move. So they're great scouts (your party doesn't get lost/delayed) or quartermasters (e.g. excellent hunters, able to feed the party along the way), or whatever.

Killing a bear is not a perilous journey, it is a scene that will play out as normal in a fictionally appropriate way. Getting to the bear's lair might be a perilous journey, but probably not.

An easy way to think about it: Undertake a Perilous Journey is like a multiplayer "Defy Danger" move specifically for travel - it describes what delays or calamities might befall the players along the way.