Senses
一来/ 一來 firstly
Used to list reasons or points, often in the pattern 一来...二来... , meaning "firstly... and secondly..."
一来/ 一來 as soon as one arrives
Used to indicate that an action happened immediately upon arrival.
一来/ 一來 by doing so
Used to refer back to a previously mentioned action or situation, meaning "in that way" or "if things go on like that".
一来/ 一來 to come once
To pay a single visit or to come over one time.