Possible Clues:

• Camels’ final resting place, maybe, leaving horse off track
• To that extent, carrier is off course
• Missing article, let us suppose, entertaining Turkey
• Up the garden path?
• Wrong answer — subsequently repeated in second test
• Gone off the right path
• Errant husband leaving resting place for Senior Service?
• Off the right course
• Like arty composition getting lost
• Off the rails