Stop being a bit hard on an officer (4)
I believe the answer is:
halt
'stop' is the definition.
(halt can mean to stop)
'a bit hard on an officer' is the wordplay.
'a bit' indicates taking the first letters (I've seen 'bits of' mean this).
'on' is a charade indicator (letters next to each other).
'an' becomes 'a'.
'officer' becomes 'lt' (abbreviation for lieutenant).
The first letter of 'hard' is 'h'.
'h'+'a'+'lt'='HALT'
'being' is the link.
(Other definitions for halt that I've seen before include "Stop; minor station" , "Pull up" , "Falter - stop" , "limping" , "Bring to a stop; lame" .)