Flashy person ice-skating circles very fast (10)
I believe the answer is:
hypersonic
'very fast' is the definition.
(I've seen this before)
'flashy person ice-skating circles' is the wordplay.
'circles' indicates the answer is hidden within the clue.
'HYPERSONIC' is hidden in the letters of 'flashy person ice skating'.
(Other definitions for hypersonic that I've seen before include "Very much faster than sound" , "likely to boom" , "lightning quick?" , "Faster than Mach 5" , "very fast" .)