A difficult problem is a challenge that requires a great deal of thought and effort to solve. The crossword solutions for this term are POSER (5 letters), Tickler (7 letters), DILEMMA (7 letters), NUT (3 letters), TOUGHIE (7 letters), and STICKLER (8 letters). POSER is a question or problem that is difficult to answer or solve. Tickler is something that is difficult to understand or solve. DILEMMA is a situation in which a difficult choice has to be made between two or more alternatives. NUT is an informal term for a difficult problem or puzzle. TOUGHIE is a difficult problem or task. STICKLER is someone who insists on very strict standards of accuracy or correctness.