A phrase used when someone needs to do a multitude of tasks before doing something else. Such as going to the bathroom, making a sandwich, finish a conversation, check Facebook, put on cosmetics, change clothes, finish chores and homework, water a plant, get a drink, grab some money, make a phone call, feed a pet, etc.
Friend: "Hey bro, you wanna go shoot some hoops?"
You: "For sure man, just hold on a mango. I gotta go finish up some stuff."