If you are getting farmed or attacked, ensure your account is always active. When he attacks you, ensure that all res and troops are sent away or been used up. Increase your markets so you can dodge res that is not able to be used before attack. Most 'leets' will leave you alone, or try and get you when your offline.
Ensure you are building O troops, you cannot build defensive troops faster than they can build offensive troops. farm and try and grow as fast as you can, both in getting LC and axes, as well as buildings. They may leave you alone, to be their nobel target.
This is where it gets tricky, virtually every good startup player is mainly O, they may have some D but not much, ensure you have a decent army before you try this. But take note of his online times and try scouting, or attacking him back. Make sure you get a group of people near him to do the same. You will decrease his income and lower his ability to make troops.
If you are an average player against a very good player, you will need people on your side, as many as you can get around him. Remember the enemy of my enemy is my friend, no matter how good the player, if you have a lot of people attacking him, you do have a good chance of winning.
