Uniform returned by marines, nothing by engineers -- not again! (9)
I believe the answer is:
nevermore
'not again' is the definition.
(I've seen this in another clue)
'uniform returned by marines nothing by engineers' is the wordplay.
'uniform' becomes 'even' (I've seen this before).
'returned' says the letters should be written backwards.
'by marines nothing' becomes 'rmo' (I can't explain this - if you can you should believe this answer much more).
'by' says to put letters next to each other.
'engineers' becomes 're' (abbreviation for Royal Engineers).
'even' backwards is 'neve'.
'neve'+'rmo'+'re'='NEVERMORE'
Can you help me to learn more?
(Other definitions for nevermore that I've seen before include "'Quoth the Raven, - - ' (Poe)" , "not to be repeated" , "At no time hereafter" , "Message delivered by raven" , "as the Raven said" .)