a busman's holiday
slang A vacation in which one does an activity that is similar to one's job (as in the case of a bus driver, or "busman," who drives on his vacation). Because I'm a docent, visiting museums on vacation is like a busman's holiday for me.
busman's holiday leisure
time spent doing something similar to what one does at work. (Alludes to a bus driver going on a bus tour for his vacation or on a day off.) Tutoring students in the evening is a busman's holiday for our English teacher. It's a bit of a busman's holiday to ask her to be wardrobe mistress for our amateur production in the summer. She's a professional dressmaker.