The Collaborative International Dictionary of English v.0.48:
Natty \Nat"ty\, a. [Cf. Neat clean.] Neatly dressed; smart; trim; tidy; spruce. [Colloq.] [1913 Webster] -- Nat"ti*ly, adv. -- Nat"ti*ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
nattily adv 1: in a natty manner; with smartness; "it was arranged carefully and nattily"