cling·y. 1. emotionally dependent: too dependent on the company or emotional support of other people. 2. sticking to body: sticking closely to the body. - from Encarta.com
I am definitely NOT clingy... and never have been. In fact, clinginess in my friends is one sure way to get me to bail.
I think that it's easy for non-NFs to misinterpret NF's behavior sometimes, and this can lead to incorrect accusations of clinginess.
For example, I can be a very intense person... especially when I'm first getting to know someone. Even after I comfortably settle in, I demand authenticity in my interpersonal relations. I seek out meaningful emotional connections with those around me. To S's, who don't share my craving for such connections, this can be a bit overwhelming to them. I think being overwhelmed by my emotional intensity could be equated with clingy even though it's something else entirely. (Ironically, my experience has been that Sensors tend to be the clingy ones.)
Also note that younger and/or insecure ENFPs can be ingratiating. This is very different from clingy I think. Ingratiating is about getting someone's affections that you don't already have. Clingy is about holding on / overly focusing on affections you already do have.