Oh, I get both skinny, more stringy curls and clumpy curls, so I can help out on this.
Here's one with skinny curls, (less clumping) but with good definition still.
Skinny curls (less clumping) and less definition/more frizz
Good clumping and definition
While I love clumping, I have learned that I can have skinnier curls that still look decent. That might be a 3B and up thing as curls tend to get skinnier the higher up the curl chain you go. Some 3b's and lower really try for more clumping as many prefer the look of fatter curls. One some 3B, 3c's and up, the curls are thinner by nature, and so they don't look stringy when thin.
As others said, you can also have too much clumping. On me, this is too much clumping.
...and that same curl broken up and umclumped
Sorry for the pic overload! I hope that it helps with visualizing clumps.