Violently destroy new instrument (4)
I believe the answer is:
nuke
'violently destroy' is the definition.
(to destroy with a nuclear bomb)
'new instrument' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'instrument' becomes 'uke' (uke is a kind of instrument).
'n'+'uke'='NUKE'
(Other definitions for nuke that I've seen before include "Drop huge bomb on" , "Nuclear weapon (sl.)" , "Destroy with a very powerful 18" , "Attack with an atomic weapon" , "Attack with H-bomb (slang abbr.)" .)