Runs into policeman with whip (4)
I believe the answer is:
crop
'whip' is the definition.
(thesaurus)
'runs into policeman' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'into' is an insertion indicator.
'policeman' becomes 'cop' (I've seen this before**).
'r' inserted into 'cop' is 'CROP'.
'with' is the link.
(Other definitions for crop that I've seen before include "Whip with loop instead of lash" , "Hairstyle; bird's pouch" , "Trim (a photograph)" , "Severe hairstyle" , "Graze" .)