The Collaborative International Dictionary of English v.0.48:

Practicer \Prac"ti*cer\, n. [Often written practiser.]
   1. One who practices, or puts in practice; one who
      customarily performs certain acts. --South.
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   2. One who exercises a profession; a practitioner.
      [1913 Webster]

   3. One who uses art or stratagem. [Obs.] --B. Jonson.
      [1913 Webster]