Ex-drinkers accepting sweet soldier's defence (8)
I believe the answer is:
apologia
'defence' is the definition.
(apologia is a kind of defence)
'ex-drinkers accepting sweet soldier's' is the wordplay.
'ex-drinkers' becomes 'aa' (Alcoholics Anonymous).
'accepting' means one lot of letters goes inside another.
'sweet' becomes 'polo' (I've seen this before**).
'soldier' becomes 'gi' (government issue or general issue).
'polo'+'gi'='pologi'
'aa' placed around 'pologi' is 'APOLOGIA'.
(Other definitions for apologia that I've seen before include "Formal defence of one's actions" , "sort of defence" , "Written defence of one's conduct" , "Personal written defence" , "Formal defence of one's conduct" .)