One Word Substitution

 A connoisseur is an expert/critic of arts, a neutral person may not necessarily resolve people's differences. An intermediary or an mediator however, settles the difference between two or more parties.

 Psychosis, neorosis and paranoia are mental disorders in which feelings of anxiety and compulsive acts dominate the personality. Narcissism specifically is the condition of inordinate fascination with oneself.

Flout means to openly defy or show contempt for rules/norms - to deliberately disregard. The similar-sounding Flaunt means to show off boastfully. Filch means to steal, flay means to whip/criticize harshly.

 Imagist is a poet who follows the early style of imaging poetry. Misantropist (antro-man, mis- a prefix meaning ill) is a hater of mankind. Masochist is a sadist. Iconoclast is derived from latin (icono-to break) someone who attacks popular beliefs.

Demeanour refers to a person's outward behavior, manner, or bearing - how they conduct themselves. Descry means to catch sight of something. Discreet means being careful/tactful. Digress means to wander off topic.

A placebo is a medicine or procedure with no active therapeutic effect, given solely to humor or reassure the patient. The other options are real medical treatments: antipyretic reduces fever, analgesic relieves pain, anesthetic causes numbness.

Genteel means affectedly polite or refined, often with an air of superiority or aristocratic pretensions - it can suggest artificial or exaggerated refinement. Gentle is mild/temperate, garble means to distort, gorge means to stuff or eat greedily.

A faux pas (French for 'false step') is a social blunder or breach of etiquette - a mistake in social behavior. Fad is a temporary trend, fait accompli is something already done, fetish is an object of obsession.

 Sacrilege is made up of sac(sacred) and ilege(a latin word which means to steal).

Exude means to discharge or display gradually - to ooze or give off (a feeling, quality, or liquid). Efface means to erase, elude means to evade, exclude means to leave out.

To 'derail' literally means to cause a train to run off the rails. Metaphorically, it means to obstruct, frustrate, or cause something to deviate from its planned course - exactly what 'one event putting another event off course' describes.

 Lair, den and cage are not restricted to small animals. A hutch is specially made for small animals.

Repent means 'to feel sorry or to regret', refuse means to deny, recant refers 'to withdraw a statement'. Retrace means to trace backwards or go back.

"The artist has a flair for painting." By saying that the artist has a 'flair', we are saying that the artist has a natural ability. Hence, 'flair' is correct.