Possible Clues:

• Sole not the sole one
• Sole is not the sole kind
• Swimmer shows sparkle keeping amazingly fit
• The sole is not the sole one
• Sole, e.g.
• Flounder, perhaps, if time cut back into fraction of second
• Perhaps sole accommodation is found in Farnborough's outskirts
• Frustrating tiff and lash out at 4 down, for example
• 1 down for one, and that's flat
• One found in 1 Across -- or in an apartment?