Resentful soldiers stuck in home counties (4)
I believe the answer is:
sore
'resentful' is the definition.
(sore can mean resentful or annoyed)
'soldiers stuck in home counties' is the wordplay.
'soldiers' becomes 'OR' (Other Ranks).
'stuck in' means one lot of letters goes inside another.
'home counties' becomes 'se' (Home Counties in the South East of England).
'or' going inside 'se' is 'SORE'.
(Other definitions for sore that I've seen before include "Painful or tender" , "Causing or suffering pain" , "Feeling pain or informally angry" , "Painfully sensitive" , "very much" .)