Quick attack to seize power (5)
I believe the answer is:
rapid
'quick' is the definition.
('rapid' can be a synonym of 'quick')
'attack to seize power' is the wordplay.
'attack' becomes 'raid' (raiding is a kind of attacking).
'to seize' indicates putting letters inside.
'power' becomes 'p'.
'raid' going around 'p' is 'RAPID'.
(Other definitions for rapid that I've seen before include "Waterway where the current runs very fast" , "Express" , "Prompt" , "Happening at great speed" , "Flying" .)