Leaders of regiment are instigating dangerous assault (4)
I believe the answer is:
raid
'assault' is the definition.
(I've seen this in other clues)
'leaders of regiment are instigating dangerous' is the wordplay.
'leaders of' suggests taking the first letters.
The initial letters of 'regiment are instigating dangerous' is 'RAID'.
(Other definitions for raid that I've seen before include "Inroad" , "Invade" , "Enter a territory and take spoils" , "Go on the attack" , "Finch and Bronson starred in . . . . On Entebbe" .)