Sentence:  Incapable of self-delusion , the Founding Fathers found the crisis of their time to be equally grave , and yet they had confidence that America would surmount it and that a republic of free peoples would prosper and serve as an example to a world <WSD>aching</WSD> for liberty . 
Meaning of the word marked with <WSD> tags:  have a desire for something or someone who is not present