えどのかたきをながさきでうつ

江戸の敵を長崎で討つ

to hit someone where they least expect it; to take revenge on someone in an unlikely place; to get revenge on someone in a different contest; to attack the Edo enemy in Nagasaki

N3Expression
Expression, Godan verb (tsu ending)
to hit someone where they least expect itto take revenge on someone in an unlikely placeto get revenge on someone in a different contestto attack the Edo enemy in Nagasaki