きれいにしておかなければ

must keep clean

→ 奇麗だ
phrase Uncommon #19,459
must keep clean Often followed by なりません or いけません to complete the expression of obligation. 〜ておく conveys keeping something in a particular state.
JA: 食べる前に、手をきれいにしておかなければなりません。
EN: You must keep your hands clean before eating.