Russian boy soldier becomes an NCO (8)
I believe the answer is:
sergeant
'an nco' is the definition.
(I've seen this before)
'russian boy soldier' is the wordplay.
'russian boy' becomes 'serge' (I am not sure about the 'russian' bit.).
'soldier' becomes 'ant' (soldier is a type of ant).
'serge'+'ant'='SERGEANT'
'becomes' is the link.
Can you help me to learn more?
(Other definitions for sergeant that I've seen before include "Military or police officer" , "NCO; Death a fell one, Hamlet" , "CARRY ON FILM" , "Rank above corporal" , "Police rank" .)