Listen up
Definition 1 of 1
Pro Tip 1/3Casual Command
Used informally to instruct a group to pay attention, not for formal settings. 
Guys, listen up - this is how we're going to win the game.
Pro Tip 2/3Authority Indicator
Indicates the speaker is in charge and is about to give important information or instructions. 
Listen up, class - we're changing the schedule today.
Pro Tip 3/3Urgency Emphasis
Implies what's coming next is urgent and requires immediate attention. 
Everyone, listen up! We need to evacuate now!