The Collaborative International Dictionary of English v.0.48:

Hamfatter \Ham"fat`ter\ (h[a^]m"f[a^]t`t[~e]r), n. [From a negro
   minstrel song called "The ham-fat man."]
   A low-grade actor or performer; a ham. [Theatrical Slang]

   Syn: ham.
        [Webster 1913 Suppl.] ham-fisted