Answer:

EXCOP

Answer	Crossword Clue
EXCOP	Joseph Wambaugh, e.g.
EXCOP	Many a security guard
EXCOP	Former sergeant, perhaps

EXCOP	One who's no longer blue?
EXCOP	Onetime police officer
EXCOP	Many a private investigator

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.