Bombardment soon over - 500 stick around (9)
I believe the answer is:
cannonade
'bombardment' is the definition.
(thesaurus)
'soon over 500 stick around' is the wordplay.
'soon' becomes 'anon' (I've seen this before).
'over' says the letters should be written backwards.
'500' becomes 'd' ('d' can be a synonym of '500').
'stick' becomes 'cane' (cane is a kind of stick**).
'around' means one lot of letters goes inside another.
'anon' in reverse letter order is 'nona'.
'nona'+'d'='nonad'
'nonad' put into 'cane' is 'CANNONADE'.
(Other definitions for cannonade that I've seen before include "Barrage" , "Period of continuous heavy gunfire" , "attack" .)