Junior officer’s regular payment to change name (9)
I believe the answer is:
subaltern
'junior officer's' is the definition.
(I've seen this before)
'regular payment to change name' is the wordplay.
'regular payment' becomes 'sub' (I have seen 'Advance payment ' mean 'sub' so perhaps 'payment' could also mean 'sub'. I am not sure about the 'regular' bit.).
'to change' becomes 'alter' ('alter' can be a synonym of 'change').
'name' becomes 'n' (common abbreviation e.g. on forms).
'sub'+'alter'+'n'='SUBALTERN'
Can you help me to learn more?
(Other definitions for subaltern that I've seen before include "Army officer below the rank of captain" , "Lesser official" , "Junior officer" .)