Possible Clues:

• Stunning
• Aunt's doing exercises -- incredible!
• Time taken by a measuring of depth is amazing
• Really impressive, spelled using only the letters of 39-Down
• With regard to finance, capital loss is staggering
• A trap to steal pound loses penny? That's surprising
• Incredible temperature detected in a measurement at sea
• Staggering time taken by a measurement of depth
• Phenomenal cockney pooch caught in a police trap
• Article with sample of opinions about tango? Staggering!