Attack with a jack, by all accounts (7)
I believe the answer is:
assault
'attack' is the definition.
(I know that attack can be written as assault)
'a jack by all accounts' is the wordplay.
'jack' becomes 'ass' (I've seen this before).
'by' says to put letters next to each other.
'all accounts' becomes 'ult' (I can't explain this - if you can you should give a lot more credence to this answer).
'a' put after 'ass' is 'assa'.
'assa'+'ult'='ASSAULT'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for assault that I've seen before include "Attack violently" , "set about" , "Storm" , "Onslaught" , "Violent attack in action or words" .)