He wrote of WWI soldiers quickly (7)
I believe the answer is:
sassoon
'he wrote of wwi' is the definition.
The definition suggests a singular noun which matches the answer.
'soldiers quickly' is the wordplay.
'soldiers' becomes 'sas' (Special Air Service).
'quickly' becomes 'soon' (I've seen this in another clue).
'sas'+'soon'='SASSOON'
Can you help me to learn more?
(Other definitions for sassoon that I've seen before include "Siegfried --, poet and writer" , "Siegfried --, English writer" , "Siegfried ---, war poet" , "Poet condemning war" , "Siegfried --, English poet and novelist" .)