Echo smart address chosen regularly for fellow soldiers (8)
I believe the answer is:
comrades
'fellow soldiers' is the definition.
(those one is fighting with)
'echo smart address chosen regularly' is the wordplay.
'chosen regularly' indicates alternate letters (letters taken at regular intervals).
'echo'+'smart'+'address'='echosmartaddress'
The alternate letters of 'echosmartaddress' are 'COMRADES'.
'for' acts as a link.
(Other definitions for comrades that I've seen before include "Associates" , "Friends or fellow-workers" , "Colleagues" , "Staunch companions, sometimes in arms" , "Friends, companions" .)