Marched in an army with Field Marshal (5)
I believe the answer is:
filed
'marched in an army' is the definition.
'filed' can be an answer for 'marched' (filing is a kind of marching). I'm not certain of the 'in an army' bit.
'field marshal' is the wordplay.
'marshal' is an anagram indicator (I've seen 'marshals' mean this (marshal can mean to gather)).
'field' with letters rearranged gives 'FILED'.
'with' is the link.
Can you help me to learn more?
(Other definitions for filed that I've seen before include "arranged in a particular way" , "Noted" , "Put away in a container for records" , "Placed in folder" , "Worked with a tool" .)