Resentment private soldier expressed vocally (7)
I believe the answer is:
rancour
'resentment' is the definition.
(I know that resentment can be written as rancour)
'private soldier expressed vocally' is the wordplay.
I cannot quite see how this works, but
'soldier' could be 'nco' (non-commissioned officer) and 'nco' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rancour that I've seen before include "Animosity" , "Bitterness and bile" , "Spite" , "Bitterness or resentfulness" , "Deep, bitter hate" .)