How to safely get down in Rise of the Tomb Raider?
I think this is right after you have collected the 'Ancient Abilities' Hunter skill, allowing you to rapidly fire two arrows after one another. You then arrived here by climbing up the Ice Ship as seen in the screenshot you posted. You don't need to go down there again, but you need to head left. There is a cable right there leading you to a different path.
See this video:
For the default keys to drop safely from a ledge, use c to drop, and e to grab on to the ledge.
Of course, this doesn't work in situations where you're not supposed to climb down.