Possible Clues:

• Don't move party when Etna erupts
• Stand still! Party animal perhaps is with Etna in a knot
• Idle horse, first to last in National
• Stand still! Party animal is not initially close to start of 9 across
• Half of country hampered by present decline
• A good neighbour's first settled in country to become sluggish
• Two stones, Newton admitted, remain motionless
• Stand still, seeing a gun unloaded in Texas, perhaps
• Stand still and become dull
• Do nothing for nation protecting a good name