Offensive cackle breaking on street (9)
I believe the answer is:
onslaught
'offensive' is the definition.
(I've seen this before)
'cackle breaking on street' is the wordplay.
'cackle' becomes 'laugh' (cackle is a kind of laugh).
'breaking' means one lot of letters goes inside another.
'street' becomes 'st' (abbreviation).
'on'+'st'='onst'
'laugh' inserted inside 'onst' is 'ONSLAUGHT'.
(Other definitions for onslaught that I've seen before include "Destructive attack" , "Hunt goals (anag) - offensive" , "Fierce attack" , "Sally" , "Heavy attack" .)