To Leave, To Walk Away, To Depart
intransitive verb, godan verb
You 立ち and then 去る. Makes sense, as in order to leave, you'll have to stand up first.
たちさる
This combines the readings of two verbs you already know, so you should be good to go here!
何も言わずに立ち去るなんて、ひどいよ。
Walking away without saying a word is not cool.
早くここから立ち去れ!
Leave this place now, quickly!
男はその場を足早に立ち去った。
The man quickly left the spot.