cover your backside/behind/rearidiomdisapprovingvery informal(also UKdisapprovingoffensivecover your arse); (also USdisapprovingoffensivecover your ass/butt)
（做某事以）保护自己的利益，不让别人抓住小辫子
to do something to protect yourself from blame or criticism in the future
This so-called enquiry is purely designed to cover their backsides.