Be somebody’s department
Definition 1 of 1
Pro Tip 1/3Responsibility Hint
Suggests who should handle a task without giving direct orders. 
You're good with numbers, so this budget report is your department.
Pro Tip 2/3Expertise Indicator
Implies someone has special skills or knowledge in an area. 
Talk to Rachel about the problem, it's her department.
Pro Tip 3/3Polite Refusal
A way to decline tasks that are outside one's role in a polite manner. 
I don't handle client accounts, that's not my department.