Keen soldier in WWI battlefield? (9)
I believe the answer is:
trenchant
'wwi battlefield?' is the definition.
I can't tell whether this defines the answer.
'keen soldier' is the wordplay.
'keen' becomes 'trench' (I can't explain this - if you can you should give a lot more credence to this answer).
'soldier' becomes 'ant' (I've seen this before).
'trench'+'ant'='TRENCHANT'
'in' is the link.
(Other definitions for trenchant that I've seen before include "blunt" , "Incisive in expression" , "Acerbic" , "biting" , "Distinctly defined" .)