HSBC Holdings has taken the unusual step of getting directly involved in pushing its Hong Kong subsidiary, Hang Seng Bank, to offload portfolios of bad real estate debt, underscoring growing concerns over the city’s struggling property sector. About two months ago, the lender directed its London-based global chief corporate credit officer and the head of its special credit unit to ensure Hang Seng started a process of selling portfolios, according to people familiar with the matter, who asked...