A phrase used when someone needs to complete a multitude of tasks before doing something else. Such as going to the bathroom, settling family quarrels, grabbing food, changing clothes, put on cosmetics, make a sandwich, finish homework, grab a beer, do chores, etc. One mango of time can depend on the person; fairly quick or a long, long time.
Friend: "Hey bro, you wanna go the basketball court and shoot some hoops?"
You: "For sure man, just hold on a mango. I gotta finish up some stuff real quick."