It is used in the expression 一旗揚げる.
He is trying to start his own business and make a name for himself.
Standard kanji spelling; primarily used in the set phrase 一旗揚げる.
Compound of 一 (one) and 旗 (flag). The exact origin of the idiomatic use is uncertain, but it likely refers to raising one's own banner as a symbol of starting a new endeavor.