Wiktionary
set to work
vb. 1 (context intransitive idiomatic English) To begin working. 2 (context intransitive idiomatic with gerund English) To begin working at. 3 (context transitive English) To cause to begin working.
Usage examples of "set to work".
I set to work, and in time I delivered to specifications, without having to strain or contort the tale.
After tonight you will remain here permanently, I expect, so you had better set to work to clear a patch of ground for your roots.
The tall one produced some macrame work from her cane handbag and set to work further on its dull design.