Be at pains to do something - Idioms by The Free Dictionary
be at pains to do something
be at pains
To put forth effort toward some goal or end. Annabelle is at pains to make sure her relatives are comfortable when they come to visit. So far, she's cleaned the whole house and set up all the guest rooms.
be at (great) pains to do something put a lot of effort into doing something correctly: The manager was at great pains to point out that no one would lose their job after reorganization. ♢ She was at pains to make us feel welcome in her home.