Crossword clue: not easy; requiring great physical or mental effort to accomplish or comprehend or endure

The most common answer is difficult (9 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

difficult 9 letters wn-def

not easy; requiring great physical or mental effort to accomplish or comprehend or endure

hard 4 letters wn-def

not easy; requiring great physical or mental effort to accomplish or comprehend or endure