"Ensurance" isn't a word, so what can I use instead?

I want a word that means exactly "The action of ensuring something."

Example sentences (with the coined word ensurance):

"The neophyte may claim competence at the task, but your ensurance of its completion would ease my mind."

"...tasked with ensurance of a clear path through the debris."

"His duties consisted primarily of ensurance rather than active personal labor."

"Ensurance" itself does not appear in the dictionary; is there another word which means exactly this that I could substitute?

("Supervision" comes close but does not always connote a promised outcome for which the supervisor is directly accountable. It's the best substitute I can think of, personally, but fails to imply an actual guarantee.)

The action of ensuring something is simply ensuring, so "..your ensuring its completion would ease my mind," and "...tasked with ensuring a clear path...," and "...his duties consisted primarily of ensuring that things were accomplished rather than active personal labor" all work well this way.

According to Merriam-Webster, "ensurance" is a word, and I quite agree.

MERRIAM WEBSTER: the act of means of ensuring.