Quick attack trapping leader of pack (5)
I believe the answer is:
rapid
'quick' is the definition.
('rapid' can be a synonym of 'quick')
'attack trapping leader of pack' is the wordplay.
'attack' becomes 'raid' (raiding is a kind of attacking).
'trapping' is an insertion indicator.
'leader of' suggests taking the first letters.
The initial letter of 'pack' is 'p'.
'raid' going around 'p' is 'RAPID'.
(Other definitions for rapid that I've seen before include "moving fast" , "Speedy, quick" , "Showing pace" , "Expeditious" , "Moving at speed" .)