The Collaborative International Dictionary of English v.0.48:

Advocation \Ad`vo*ca"tion\, n. [L. advocatio: cf. OF. avocation.
   See Advowson.]
   1. The act of advocating or pleading; plea; advocacy.
      [Archaic]
      [1913 Webster]

            The holy Jesus . . . sits in heaven in a perpetual
            advocation for us.                    --Jer. Taylor.
      [1913 Webster]

   2. Advowson. [Obs.]
      [1913 Webster]

            The donations or advocations of church livings.
                                                  --Sanderson.
      [1913 Webster]

   3. (Scots Law) The process of removing a cause from an
      inferior court to the supreme court. --Bell.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ADVOCATION, Scotch law. A writing drawn up in the form of a petition, called
a bill of advocation, by which a party in an action applies to the supreme
court to advocate its cause, and to call the action out of an inferior court
to itself. Letters of advocation, are the decree or warrant of the supreme
court or court of sessions, discharging the inferior tribunal from all
further proceedings in the matter, and advocating the action to itself.
This proceeding is similar to a certiorari (q.v.) issuing out of a superior
court for the removal of a cause from an inferior.