Sentence:  If a man is overburdened, which is the true cause of complaint, or <WSD>underburdened</WSD>, which is the modern cause of complaint, he may seek redress; but he alone who is overburdened or <WSD>underburdened</WSD> is authorised to seek redress. 
Meaning of the word marked with <WSD> tags:  To assign less work than someone or something is capable of.