Soldiers get together to reminisce (9)
I believe the answer is:
recollect
'reminisce' is the definition.
(I've seen this before)
'soldiers get together' is the wordplay.
'soldiers' becomes 're' (Royal Engineers).
'get together' becomes 'collect' ('collect' can be a synonym of 'get together').
're'+'collect'='RECOLLECT'
'to' acts as a link.
(Other definitions for recollect that I've seen before include "Call to mind" , "Bring back to mind." , "Remember" , "Recall to mind" , "Flock together again" .)