it' usually used to describe a kind of statement when you worry about sth or sb. [directly translated into English is : your heart is dangling that cannot go back to where it should be] eg. Mary;s husband is a soldier in the war, Mary的心一直悬着的/Mary的心悬着没有着落 (Mary's heart keeps dangling/ Mary's heart is dangling. ,[because she worries about her husband] ) :) here “一颗” can be removed, "悬着一颗心没着落" ,this kind of expression you can only use in the articles because it's too literary)

like Tenterhooks

It means "worry about something very much", don't know what is the result or what is the answer or what to do...