From Longman Dictionary of Contemporary Englishtour of dutyˌtour of ˈduty noun (plural tours of duty) [countable] BECPERIOD OF TIMEa period of time when you are working in a particular place or job, especially abroad while you are in the army etc
Examples from the Corpus
tour of duty• But Mr Sandy found it a stimulating, not to say exhausting, tour of duty.• Her tour of duty is almost done.• He said his tour of duty ended at 10: 45.• The two had enjoyed a eight-month affair, but McAllister's tour of duty in Ulster was ending.• I am here for a year, and this is my second tour of duty.• During a recent three-year tour of duty as a newspaper correspondent in the Middle East I found abundant cause for both. 