He has a way of looking after a joint right (7)

I believe the answer is:

janitor

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Other definitions for janitor that I've seen before include "One employed to clean and maintain a building" , "Caretaker or doorkeeper" , "Caretaker (mainly US)" , "(In Scotland) school caretaker" , "Person looking after building" .)

Want a hint initially instead of a full solution? Install my app