Discharge from colossal vocabulary (5)
I believe the answer is:
salvo
'discharge' is the definition.
(I've seen this before)
'from colossal vocabulary' is the wordplay.
'from' indicates a hidden word.
'SALVO' can be found hidden inside 'colossal vocabulary'.
(Other definitions for salvo that I've seen before include "concentrated fire" , "Series of shots" , "Burst of rapid fire" , "Simultaneous discharge of fire" , "Several rounds" .)