Solution

LOOKOUT

3 clues

Observation post

Word class: Common noun
Nature of clue: Description
Difficulty: Easy
Sources: Boatload Puzzles
Topics: Building - Construction - Architecture

Scenic viewpoint

Word class: Common noun
Nature of clue: Description
Difficulty: Easy
Sources: Boatload Puzzles
Topics: Geography, Travel

Sentry

Word class: Common noun
Nature of clue: Synonym
Difficulty: Very easy
Sources: Boatload Puzzles
Topics: Society

Other solutions to Sentry

Words are categorized by artificial intelligence: there can be mistakes.