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.)