Provisional allowances for serving men (4,7)
I believe the answer is:
army rations
'serving men' is the definition.
The definition suggests a plural noun which matches the answer.
'provisional allowances' is the wordplay.
'provisional' becomes 'army' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'allowances' becomes 'rations' (I've seen this in another clue).
'army'+'rations'='ARMY RATIONS'
'for' is the link.
Can you help me to learn more?
(Another definition for army rations that I've seen is " Food".)