Stop being mean (5)
I believe the answer is:
close
This clue is a double definition.
'stop' is the first definition.
(I know that close is a more specific form of the action stop)
'being mean' is the second definition.
(I've seen this before)
(Other definitions for close that I've seen before include "Meeting with a UFO?" , "Dense; nearby" , "Stop proceedings" , "Cathedral's precincts" , "cathedral precinct" .)