Possible Clues:

• Dimwit
• At the present time
• Amusing or stupid? One's the latter
• Sign - or a museum will accept a person knowing nothing!
• Person knowing little criminal roaming America
• 'Nyet' not yet accepted by Russian author, having not begun 'The Idiot'
• Dull type
• Wry or amusing dunce
• He knows nothing of smog (untreated) and air pollution
• One doesn't know if it's amusing or outrageous