Dickens's titular friend (6)
I believe the answer is:
mutual
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for mutual that I've seen before include "Joint < commonly" , "Dickens novel 'Our . . . . . . Friend'" , "Shared by two or more people" , "Feeling for each towards the other" , "Given and returned" .)