What do you do if you play a champion that lacks reliable wave clear...
and has to farm the next minion wave under the turret 
and has to farm the next minion wave under the turret 
Learn how to prep the wave before it gets to the tower. And then learn and practice how to CS under tower. This is an extremely valuable skill on every champion. Not only ones with low waveclear.
Farm until you can kill your lane opponent, then push the wave as fast as you can.
Farm until you can kill your lane opponent, then push the wave as fast as you can.
Yes, this is... good advice.