Bankrupt, basically, which often leads a company going bust.
Wikipedia says: Administration is a procedure to protect a company from its creditors in order for it to be able to make significant operational changes or restructuring so that it could continue as a going concern, or at least in order to achieve a better outcome for creditors than via liquidation. In contrast to Chapter 11 in the US where the directors remain in control throughout that restructuring process, in the UK an Administrator is appointed who must be a licensed Insolvency Practitioner to manage the company's affairs to protect the creditors of the insolvent company and balance their respective interests. Unless the company itself is saved by this process, the company is subsequently put into liquidation to distribute the remaining funds.