Soldier gaining new spirit (3)
I believe the answer is:
gin
'spirit' is the definition.
(I've seen this before)
'soldier gaining new' is the wordplay.
'soldier' becomes 'gi' (government issue or general issue**).
'gaining' means one lot of letters go next to another.
'new' becomes 'n'.
'gi'+'n'='GIN'
(Other definitions for gin that I've seen before include "Spirit, aka 'Mother's ruin'" , "Alcohol for the snare" , "Alcoholic drink once known as mother's ruin" , "A short" , "It could be used for drinking" .)