Possible Clues:

• Evasive, elusive
• Hard to pin down
• Hard to grasp or walk on
• Descent into sin in this sort of slope
• Thrash youngster first for being evasive
• Shifty and direly sly piper
• Like an eel
• Evasive - awkward to walk on
• Evasive like an eel
• Mule you've initially found difficult to get hold of