Very fast unexpected attack grabbing power (5)
I believe the answer is:
rapid
'very fast' is the definition.
(I've seen this before)
'unexpected attack grabbing power' is the wordplay.
'unexpected attack' becomes 'raid'.
'grabbing' is an insertion indicator.
'power' becomes 'p'.
'raid' going around 'p' is 'RAPID'.
(Other definitions for rapid that I've seen before include "Electrical connector" , "Quickly accomplished" , "Speedy (5)" , "Happening at great speed" , "Fleet, swift" .)