Interfere in someone else's business (6)
I believe the answer is:
meddle
'interfere in someone else's business' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for meddle that I've seen before include "Mess with" , "Stick one's oar in" , "Intrude in other people's affairs" , "Tamper, tinker" , "Interfere or tinker" .)