Answer:

spyhole

Answer	Crossword Clue
SPYHOLE	Secret observer's opening
SPYHOLE	What a peeper uses to peep
SPYHOLE	Peeping Tom's spot

SPYHOLE	Door opening for peeping
SPYHOLE	Peeping aid

Crossword

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