avoid even the appearance of impropriety; leave no room for scandal
A yojijukugo proverb meaning one should avoid situations that could invite suspicion, even if innocent. Literally: 'in a melon field, don't adjust your shoes; under a plum tree, don't straighten your hat' — actions that could be misinterpreted as stealing.
To avoid any suspicion, he left the scene.
公務員は瓜田李下の行動を慎むべきだ。
Public officials should refrain from actions that could invite suspicion.
A related proverb with the same meaning, often used together with 瓜田に履を納れず to form the full expression behind 瓜田李下.
From a Chinese proverb: 瓜田不納履，李下不整冠 (In a melon field, do not put on your shoes; under a plum tree, do not adjust your hat). The Japanese yojijukugo 瓜田李下 condenses this into four characters.