One grabbed by policeman and shot (3)
I believe the answer is:
pic
'shot' is the definition.
(short for picture)
'one grabbed by policeman' is the wordplay.
'one' becomes 'i' (Roman numeral).
'grabbed by' is an insertion indicator (inserted letters are grabbed inside).
'policeman' becomes 'pc' (police constable).
'i' put into 'pc' is 'PIC'.
'and' acts as a link.
(Other definitions for pic that I've seen before include "Image (abbr)" , "Photo (informal)" , "Snapshot" , "Photo (colloq.)" , "illustration" .)