Sentence:  The familiarity of Sydney Smith's manner does not consist merely in his style ; indeed, the terseness and brilliancy of his diction, though not at all artificial in appearance, could not have been attained without labor and <WSD>solicitude</WSD> ;—but it is the result of the blunt, fearless, severe, yet good-humored, nature of the man. 
Meaning of the word marked with <WSD> tags:  The state of being solicitous; uneasiness of mind occasioned by fear of evil or desire for good; anxiety.