Sentence:  The <WSD>skill</WSD> was not in creating a grid full of words, but in producing clues cryptic enough to baffle the puzzler, yet constructed so honestly that they could be solved by any intelligent person who knew the conventions. 
Meaning of the word marked with <WSD> tags:  Capacity to do something well; technique, ability. Skills are usually acquired or learned, as opposed to abilities, which are often thought of as innate.