The ordinary soldier's pay? (7,6)
I believe the answer is:
private income
'the ordinary' is the definition.
Both the answer and definition are singular nouns.
Perhaps they are linked in a way I don't understand?
'soldier's pay?' is the wordplay.
'soldier' becomes 'private' (private is a type of soldier).
'pay?' becomes 'income' (I've seen this before).
'private'+'income'='PRIVATE INCOME'
Can you help me to learn more?
(Another definition for private income that I've seen is " Money from investments etc".)