Endless preparation by old group of big shots (5)
I believe the answer is:
salvo
'shots' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for salvo that I've seen before include "Discharge of weapons in unison" , "Simultaneous burst of gunfire" , "Fusillade, volley" , "Burst (of applause, insults, artillery etc)" , "Simultaneous discharge of artillery" .)