Rise, lest soldiers get captured (8)
I believe the answer is:
increase
'rise' is the definition.
(I know this)
'lest soldiers get captured' is the wordplay.
'lest' becomes 'in case' (as in 'lest we forget').
'soldiers' becomes 'RE' (Royal Engineers).
'get captured' is an insertion indicator.
'incase' placed around 're' is 'INCREASE'.
(Other definitions for increase that I've seen before include "extra money at work" , "Grow bigger" , "Profit" , "Make or grow larger" , "Become greater in size" .)