Wiktionary
work at
vb. (context transitive English) To make a physical or mental effort to progress some specified task
WordNet
work at
v. to exert effort in order to do, make, or perform something; "the child worked at the multiplication table until she had it down cold" [syn: work on]
Usage examples of "work at".
Oh yes, he was busier than his brother could possibly know, and he had to do everything by himself, without any help from a crew of clerks and stenographers such as Myron had, so that Myron could sit on his bottom and never do any real work at all.