Quick tip: You can use Leona passive on the wave to clear faster

Let Leona use her W/E before the ADC uses their waveclear. If you kill the enemy laner or forced them to back, you should shove the wave, right? Use Leona's damage on top of that. Leona's E has 60 damage at rank 1, so assuming pre-6, that's like extra 100 damage on minions. Even more with her W (although its delay and high damage will mean she'll take some CS). You'll push faster, go back faster, deny more, and come back faster.

(This may not work well in solo queue, since, communicating details quickly is difficult. In a premade, try to do this all the time.)