The word "evidently" is correct and usable in written English. It is an adverb meaning "in an obvious way; clearly." For example, you can use it in a sentence like this: "Evidently, they had been planning the trip for a while now.".

Examples of Evidently in a sentence The defendant was evidently guilty of the crime since there was so much direct DNA evidence and witness statements against him. With all straight A’s and the best quarterback on the football team, the young man would evidently get a full scholarship to the local university.