We soldiers lived here (4)
I believe the answer is:
were
'lived here' is the definition.
The answer and definition can be both to do with fundamental existence as well as being past participle verbs.
Perhaps you can see an association between them that I can't see?
'we soldiers' is the wordplay.
'soldiers' becomes 're' (Royal Engineers).
'we'+'re'='WERE'
Can you help me to learn more?
(Other definitions for were that I've seen before include "(You/we/they) existed" , "SECOND PART OF 14" , "'Are, in the past (4)'" , "Existed in the past" , "Lycanthrope" .)