Possible Clues:

• Involving a single dimension
• Starts to lead imposingly, approaching straight
• Having one dimension
• As a Just A Minute speech may be: artful, in earshot, making a case
• Some criminal, in earnest, going straight
• One-dimensional row disheartened Arthur
• Foolish king put outside home in a row
• Half life is close to being absolutely straight
• Like some Cretan scripts nonsensical poet keeps at home
• Involving or having a single dimension