Possible Clues:

• Staying power?
• Sloth - I underrate it, as being odd
• Mechanics concept
• I earn it (anag.)
• I tire with an awful inclination not to budge
• Resis-tance to change
• Lack of action, but in time it returns
• I retain (anag) - the tendency to retain same speed and direction
• Physics concept
• Property of matter