I got the KEY to the army car in my hand, and I am brandishing it.
reveal the extent of one's power
発 (launch) + 揮 (brandish)
= 発揮 (reveal the extent of one's power)
to reveal one's true strength, to get an opportunity to exercise one's full power (in economics, language ability, fighting, whatever)
conductor or commander
指 (finger / point at) + 揮 (brandish) + 者 (professional)
= 指揮者 (conductor or commander)