Subordinate against attack I abandoned (6)
I believe the answer is:
vassal
'subordinate' is the definition.
(I've seen this in another clue)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for vassal that I've seen before include "Feudal landholder" , "Subordinate landholder" , "Person totally subordinated by another" , "Feudal underling" , "He owed allegiance and service to a feudal lord" .)