The Collaborative International Dictionary of English v.0.48:

Sportingly \Sport"ing*ly\, adv.
   In sport; sportively.
   [1913 Webster]

         The question you there put, you do it, I suppose, but
         sportingly.                              --Hammond.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sportingly
    adv 1: so as to be sporting; in a sporting manner [ant:
           unsportingly]