I like to donate cards to my clan for the gold and exp, but is there a disadvantage to leveling up while still in lower level arenas? I donate often so I am almost level 7 and only in Arena 4/5. Is there a drawback to being such a high level in a lower level Arena?
Your level only affects the HP and damage of your towers. There is no other effect of your level.
As you can see, there isn't any disadvantage to having a high level. This applies to all arenas.
It may also have a demoralizing effect on your opponent, if they're level or two lower. (Less on later on where levels even out and people realize that the cards and strategies play much larger role than a 100 or so more HP on the tower.)
It's not about any of that. What does it require to level up? It requires large amounts of upgrades, so if you fight someone who's a high level than you then they have stronger cards. And sometimes tier cards; meaning someone could bring hog rider from arena 4 to 3 and have an advantage. Many higher level players are losing their place in clash, and cause others to lose because they still have higher tier cards. It's a huge domino effect.