Solution

WATCHMAN

3 clues

Guard on duty

Word class: Common noun
Nature of clue: Description
Difficulty: Easy
Sources: Boatload Puzzles
Topics: Society

Night guard

Word class: Common noun
Nature of clue: Description
Difficulty: Very easy
Sources: Boatload Puzzles
Topics: Society
Number of words: 2

Sentry

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

Other solutions to Sentry

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