A bit of a…
Definition 1 of 2
Pro Tip 1/3Emphasizing Modesty
Used when downplaying your skills or achievements in a modest way. 
I'm a bit of a pianist, but I'm not ready for concerts.
Pro Tip 2/3Softening Statements
Helps make a critical comment less direct or severe. 
He's a bit of a slow worker, but very thorough.
Pro Tip 3/3Tone of Playfulness
Adds a playful tone when describing character traits or habits. 
My sister's a bit of a prankster – always joking around.