Very fast form of percussion (10)
I believe the answer is:
supersonic
'very fast' is the definition.
(I've seen this before)
'form of percussion' is the wordplay.
'form of' indicates anagramming the letters (the letters need to be in another 'form').
'percussion' anagrammed gives 'SUPERSONIC'.
(Other definitions for supersonic that I've seen before include "moving very fast" , "Faster than the speed of sound" , "Very fast - 11 (anag)" , "Faster than Mach 1" .)