Playful bow (4)
I believe the answer is:
arch
This clue is a double definition.
'playful' is the first definition.
(I've seen this before)
'bow' is the second definition.
(both can mean to curve)
(Other definitions for arch that I've seen before include "part of fingerprint" , "Self-consciously playful or teasing" , "Curved vault" , "Curve of a bridge" , "Curved entrance" .)