Attacked and brought back spoils by sea (7)

'attacked' is the definition.
(storming is a kind of attacking)

'brought back spoils by sea' is the wordplay.
'brought back' shows that the letters should be reversed in order.
'spoils' becomes 'rots' (I've seen this in another clue).
'by' is a charade indicator (letters next to each other).
'sea' becomes 'med' (short for Mediterranean).
'rots' reversed gives 'stor'.
'stor'+'med'='STORMED'

'and' acts as a link.