Solution

FUNDAMENTAL

2 clues

Basic

Word class: Common adjective
Nature of clue: Synonym
Difficulty: Very easy
Sources: Boatload Puzzles

Other solutions to Basic

Essential

Word class: Common adjective
Nature of clue: Synonym
Difficulty: Very easy
Sources: Boatload Puzzles

Other solutions to Essential

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