Wiktionary
work on
vb. 1 (context transitive English) to shape, form or improve something 2 (context transitive English) to exercise influence on someone
WordNet
Usage examples of "work on".
What is not common knowledge is that next day, with the house-wreckers already at work on the roof of the Pierre Ronsard, Myron returned to it and, sitting on a very little box in front of a very big box, finished up the final report for the Elphinstone central office of the chief accountant, who had gone home the day before, and that he showed his inescapable unromanticism by whistling over the forms and looking altogether more cheerful than when he had danced through the lobby with ledger leaves in his hair.