Inexperienced soldiers overwhelmed by information (5)
I believe the answer is:
green
'inexperienced' is the definition.
(similar in meaning)
'soldiers overwhelmed by information' is the wordplay.
'soldiers' becomes 're' (Royal Engineers).
'overwhelmed by' indicates putting letters inside (inserted letters get absorbed or overwhelmed).
'information' becomes 'gen' (gen can informally mean information).
're' inserted inside 'gen' is 'GREEN'.
(Other definitions for green that I've seen before include "Money" , "The colour of envy" , "Ecologically sound" , "Grassy area; naive" , "The colour of inexperience" .)