on the ball

on the ball - well-informed, clever, intelligent

on the blink

broken

on the cards

on the cards - likely to happen

on the case

on the case - dealing with something, trying to resolve something

on the case

doing what needs to be done

on the fly

on the fly - very quickly, without time to think

on the go

on the go - always busy or active

on the grapevine

to hear about something via rumours

on the hoof

on the hoof - to do something quickly without time to think or prepare

on the house

on the house - free or complimentary