Fixed allowances of food (7)
I believe the answer is:
rations
This clue could be a double definition.
'fixed allowances' is the first definition.
'rations' can be an answer for 'allowances' (I've seen this before). I'm not sure about the 'fixed' bit.
'food' is the second definition.
(rations is a kind of food)
'of' acts as a link.
Can you help me to learn more?
(Other definitions for rations that I've seen before include "Limits (supplies)" , "fixed allowance" , "Food allowances" , "Commons" , "Food as issued" .)