The Collaborative International Dictionary of English v.0.48:
Archly \Arch"ly\, adv. In an arch manner; with attractive slyness or roguishness; slyly; waggishly. [1913 Webster] Archly the maiden smiled. --Longfellow. [1913 Webster]WordNet (r) 3.0 (2006):
archly adv 1: in_an_arch_manner; with playful slyness or roguishness