"Clumsy" lacking dexterity, nimbleness, or grace
When you're clumsy, you might easily drop things, trip over things, bump into things, etc. I"m very clumsy myself.
Saying that someone "a bit on the clumsy side" is a way of saying they are a bit clumsy. Maybe not totally clumsy, but not very dexterous or athletic. It could be deliberate understatement though, to mean very clumsy indeed.