The quotient producing an endless fixed allowance (5)
I believe the answer is:
ratio
'the quotient' is the definition.
(I've seen this before)
'an endless fixed allowance' is the wordplay.
'an endless' means to remove the last letter.
'fixed allowance' becomes 'ration' (a fixed quota given out to someone).
'ration' with its last letter removed is 'RATIO'.
'producing' acts as a link.
(Other definitions for ratio that I've seen before include "2:1, for example" , "Relation between two things, numbers say" , "nine-to-five, say" , "One to one - maybe" , "Percentage" .)