遊あそび半はん分ぶん

na-adjective, noun which may take the genitive case particle 'no'

half in fun; not entirely serious

Describes doing something with a playful, non-serious attitude, often implying that the action is not meant to be taken fully seriously.

• 彼かれは遊あそび半はん分ぶんで料りょう理りを始はじめたが、今いまではプロ並なみだ。

  He started cooking half in fun, but now he's as good as a pro.

• 遊あそび半はん分ぶんの気き持もちで株かぶを買かってはいけない。

  You shouldn't buy stocks with a half-serious attitude.