expression
coming; going; being (somewhere); being (doing something)
Honorific abbreviation of いらっしゃって, used as a polite て-form of いらっしゃる. Covers respectful 'coming', 'going', 'being', and auxiliary 'being (doing)'.
先生はもういらしてますか。
Has the teacher already arrived?
お客様がいらして、すぐに会議室へ案内した。
The client came, and I immediately showed them to the meeting room.
部長はただ今外出していらして、午後には戻られます。
The department head is currently out, but will return in the afternoon.